Abstract xenobiotics and protective capabilities of organisms. Mechanism of the body’s defense against xenobiotics Entry of xenobiotics into the animal’s body
With the development of industrial society, changes occurred in the formation of the biosphere. Many foreign substances, the product of human activity, have entered the environment. As a result, they affect the life activity of all living organisms, including ours.
What are xenobiotics?
Xenobiotics are synthetic substances that have a negative effect on any organism. This group includes industrial waste, household products (powders, dishwashing detergents), construction materials, etc.
A large number of xenobiotics are substances that accelerate the appearance of crops. It is very important for agriculture to increase the crop’s resistance to various pests, as well as to give it a good appearance. To achieve this effect, pesticides are used, which are substances foreign to the body.
Construction materials, glue, varnishes, household goods, food additives - all these are xenobiotics. Oddly enough, some biological organisms, for example, viruses, bacteria, helminths, also belong to this group.
How do xenobiotics affect the body?
Substances that are foreign to all living things have a detrimental effect on many metabolic processes. For example, they can stop the functioning of membrane channels, destroy functionally important proteins, destabilize the plasmalemma and cell wall, and cause allergic reactions.
Any organism is adapted to one degree or another to eliminate toxic poisons. However, large concentrations of the substance cannot be completely removed. Metal ions, toxic organic and inorganic substances eventually accumulate in the body and after a certain period of time (often several years) lead to pathologies, diseases, and allergies.
Xenobiotics are poisons. They can penetrate the digestive system, respiratory tract, and even through intact skin. Routes of entry depend on the state of aggregation, structure of the substance, as well as environmental conditions.
Through the nasal cavity with air or dust, gaseous hydrocarbons, ethyl and methyl alcohols, acetaldehyde, hydrogen chloride, ethers, and acetone enter the body. Phenols, cyanides, and heavy metals (lead, chromium, iron, cobalt, copper, mercury, thallium, antimony) penetrate the digestive system. It is worth noting that microelements such as iron or cobalt are necessary for the body, but their content should not exceed a thousandth of a percent. In higher doses they also lead to negative effects.
Classification of xenobiotics
Xenobiotics are not only chemical substances of organic and inorganic origin. This group also includes biological factors, including viruses, bacteria, pathogenic protists and fungi, and helminths. Oddly enough, but such as noise, vibration, radiation, radiation also belong to xenobiotics.
According to their chemical composition, all poisons are divided into:
- Organic (phenols, alcohols, hydrocarbons, halogen derivatives, ethers, etc.).
- Organoelement (organophosphorus, organomercury and others).
- Inorganics (metals and their oxides, acids, bases).
Based on their origin, chemical xenobiotics are divided into the following groups:
Why do xenobiotics affect health?
The appearance of foreign substances in the body can seriously affect its performance. An increased concentration of xenobiotics leads to the appearance of pathologies and changes at the DNA level.
Immunity is one of the main protective barriers. The influence of xenobiotics can extend to the immune system, interfering with the normal functioning of lymphocytes. As a result, these cells do not function properly, which leads to a weakening of the body's defenses and the appearance of allergies.
The cell genome is sensitive to the effects of any mutagen. Xenobiotics, penetrating into a cell, can disrupt the normal structure of DNA and RNA, which leads to the appearance of mutations. If the number of such events is large, there is a risk of developing cancer.
Some poisons act selectively on the target organ. Thus, there are neurotropic xenobiotics (mercury, lead, manganese, carbon disulfide), hematotropic (benzene, arsenic, phenylhydrazine), hepatotropic (chlorinated hydrocarbons), nephrotropic (cadmium and fluorine compounds, ethylene glycol).
Xenobiotics and humans
Economic and industrial activities have a detrimental effect on human health due to the large amount of waste, chemicals, and pharmaceuticals. Xenobiotics are found almost everywhere today, which means that the likelihood of them entering the body is always high.
However, the most powerful xenobiotics that people encounter everywhere are drugs. Pharmacology as a science studies the effect of drugs on a living organism. According to experts, xenobiotics of this origin are the cause of 40% of hepatitis, and this is no coincidence: the main function of the liver is to neutralize poisons. Therefore, this organ suffers the most from large doses of drugs.
Prevention of poisoning
Xenobiotics are substances foreign to the body. The human body has developed many alternative pathways to eliminate these toxins. For example, poisons can be neutralized in the liver and released into the environment through the respiratory, excretory systems, sebaceous, sweat and even mammary glands.
Despite this, the person himself must take measures to minimize the harmful effects of poisons. First, you need to choose your food carefully. Group “E” supplements are strong xenobiotics, so the purchase of such products should be avoided. You shouldn’t choose fruits and vegetables just by appearance. Always pay attention to the expiration date, because after it expires, poisons form in the product.
It is always worth knowing when to stop taking medications. Of course, for effective treatment this is often a necessary necessity, but make sure that this does not develop into systematic unnecessary consumption of pharmaceuticals.
Avoid working with hazardous reagents, allergens, and various synthetic substances. Minimize the impact of household chemicals on your health.
Conclusion
It is not always possible to observe the harmful effects of xenobiotics. Sometimes they accumulate in large quantities, turning into a time bomb. Substances foreign to the body are harmful to health, which leads to the development of diseases.
Therefore, remember the minimum preventive measures. You may not notice any negative effects right away, but after a few years, xenobiotics can lead to serious consequences. Don't forget about this.
Major inorganic and organic xenobiotics common in biosphere
Vanadium
Vanadium compounds are used in the metallurgical, mechanical engineering, textile and glass industries; in the form of ferrovanadium it is used for the production of steel and cast iron.
The main routes of entry into the human body are respiratory organs, excretion mainly through urine.
Vanadium and its compounds are necessary for normal human life. They have an insulin-saving effect, reduce the level of glucose and lipids in the blood, and normalize the activity of liver enzymes.
In excess amounts, vanadium compounds have a genotoxic effect (causing chromosomal aberrations), can disrupt basic metabolism, selectively inhibit or activate enzymes involved in phosphate metabolism, cholesterol synthesis, and can change the normal composition of protein fractions in the blood (increase the amount of free amino acids). 4- and 5-valent vanadium is capable of forming complex compounds with a large number of biologically active substances: ribose, AMP, ATP, serine, albumin, ascorbic acid.
Vanadium compounds come into contact with the surface of cell membranes, in particular red blood cells, disrupting its permeability and can cause cell death.
Based on the nature of damage to organs and tissues, vanadium compounds can be classified as generally toxic poisons. They cause damage to the cardiovascular, respiratory, and central nervous systems. Symptoms of acute poisoning with vanadium compounds are similar to attacks of bronchial asthma.
Chronic poisoning with vanadium compounds is characterized by headache, dizziness, pale skin, conjunctivitis, cough sometimes with bloody sputum, nosebleeds, trembling of the limbs (tremor). The most severe clinical picture occurs when inhaling fumes and dust from the production of V 2 O 3 (this compound is used as a mordant in the textile industry) and can be fatal.
Cadmium
Widely used to produce cadmium pigments necessary for the production of varnishes, paints, and dish enamels. Its sources can be local emissions from industrial complexes, metallurgical plants, smoke from cigarettes and chimneys, and car exhaust gases.
Accumulating in the natural environment, cadmium enters the human body through food chains. Its sources are animal products (pork and beef kidneys, eggs, seafood, oysters) and plant origin (vegetables, berries, mushrooms, especially meadow champignons, rye bread). A lot of cadmium is contained in cigarette smoke (one smoked cigarette enriches the smoker’s body with 2 mg of cadmium).
Cadmium has a polytropic effect on the body.
Cadmium has a high affinity for nucleic acids, causing disruption of their metabolism. It disrupts DNA synthesis, inhibits DNA polymerase, and interferes with the addition of thymine.
The enzymatic toxic effect of cadmium is manifested primarily in the ability to block SH groups in oxyreductase and succinate dihydrogenase, choline acceptors. Cadmium is able to change the activity of catalase, alkaline phosphatase, cytochrome oxidase, carboxypeptidase, and reduce the activity of digestive enzymes, in particular trypsin.
At the cellular level, an excess amount of cadmium leads to an increase in smooth ER, changes in mitochondrial membranes, and an increase in lysosomes.
The targets in the human body are the nervous, excretory, and reproductive systems. Cadmium penetrates well through the placenta, can cause spontaneous abortions (L. Chopikashvili, 1993) and, along with other heavy metals, contribute to the development of hereditary pathology.
After reaching a cadmium concentration of 0.2 mg/kg body weight, symptoms of poisoning appear.
Acute cadmium poisoning can manifest as toxic pneumonia and pulmonary edema.
Chronic poisoning manifests itself in the form of hypertension, pain in the heart, kidney disease, pain in bones and joints. Characterized by dry and flaky skin, hair loss, nosebleeds, dry and sore throat, and the appearance of a yellow border on the neck of the teeth.
Manganese
Manganese is widely used in the steel and iron production industries, in electric welding, in paint and varnish production, and in agriculture when feeding farm animals.
Routes of entry are primarily through the respiratory system, but can penetrate the gastrointestinal tract and even intact skin.
Manganese is deposited in brain cells, parenchymal organs, and bones.
In the body, manganese is involved in the stabilization of nucleic acids, participates in the processes of reduplication, repair, transcription, oxidative phosphorylation, synthesis of vitamins C and B1, enhances metabolism, and has a lipotropic effect. It regulates the processes of hematopoiesis, mineral metabolism, growth and reproduction processes. When manganese and its compounds enter the human body over a long period of time and in large quantities, they have a toxic effect.
Manganese has a mutagenic effect. It accumulates in mitochondria, disrupts energy processes in the cell, and can inhibit the activity of lysosomal enzymes, adenazine phosphatase and others.
Manganese has a neurotoxic, allergic effect, disrupts the function of the liver, kidneys, and thyroid gland. Women exposed to manganese for a long time experience menstrual irregularities, spontaneous abortions, and the birth of premature babies.
Chronic poisoning with manganese compounds manifests itself
the following symptoms: increased fatigue, muscle pain, especially in the lower extremities, apathy, lethargy, lethargy.
Mercury
Mercury can be released into the environment from industrial wastewater from plastic manufacturing plants. caustic soda, chemical fertilizers. In addition to this, sources
mercury are: floor mastic, ointments and creams for softening the skin, amalgam fillings, water-based paints, photographic film.
Routes of entry into the body are mainly through the gastrointestinal tract, often with seafood (fish, shellfish), rice, etc. Excreted from the body by the kidneys.
Mercury has a genotoxic effect, causing DNA damage and gene mutations. Embryotoxic, teratogenic (failure to carry a pregnancy to term, birth of children with developmental abnormalities) and carcinogenic effects have been proven. Mercury has an affinity for the nervous and immune systems. Under the influence of mercury, the number of T-lymphocytes decreases and autoimmune glomerulonephritis can develop.
Mercury poisoning leads to the development of Minamato disease.
In 1953, in Japan in the Minamato Bay area, 120 people fell ill from mercury poisoning, of whom 46 died.
The clinical picture usually begins after 8-24 hours and is expressed by general weakness, fever, redness of the pharynx, and a dry cough without sputum. Then stomatitis (inflammatory processes of the oral cavity), abdominal pain, nausea, headache, insomnia, depression, inadequate emotional reactions, and fears appear.
Lead
The main sources of lead are car exhaust, aircraft engine emissions, old paint on houses, water flowing through lead-lined pipes, and vegetables grown near highways.
The main routes of entry into the body are the gastrointestinal tract and respiratory organs.
Lead is a cumulative poison; it gradually accumulates in the human body, in bones, muscles, pancreas, brain, liver and kidneys.
The toxicity of lead is associated with its complexing properties. The formation of complex compounds of lead with proteins, phospholipids and nucleotides leads to their denaturation. Lead compounds inhibit the energy balance of the cell.
Lead has a membrane-damaging effect; it accumulates in the cytoplasmic membrane and membrane organelles.
The immunotoxic effect is manifested in a decrease
nonspecific resistance of the body (decreased activity of salivary lysozyme, bactericidal activity of the skin).
The mutagenic and carcinogenic effects of lead have been proven.
Lead poisoning can manifest itself with the following symptoms: loss of appetite, depression, anemia (lead reduces the rate of formation of red blood cells in the bone marrow and blocks the synthesis of hemoglobin), convulsions, fainting, etc.
Lead poisoning in children can result in death in severe cases or, in moderate cases, mental retardation.
Chromium
Chromium compounds are widely used in the national economy, in the metallurgical and pharmaceutical industries, in the production of steel, linoleum, pencils, photography, etc.
Routes of entry: respiratory organs, gastrointestinal tract, can be absorbed through intact skin. It is secreted by all excretory organs.
In biological doses, chromium is a constant and necessary component of various tissues and is actively involved in the processes of cellular metabolism.
Entering the body in excess concentrations, chromium accumulates in the lungs, liver and kidneys.
Mechanism of pathogenic action.
Entering the cell, chromium compounds change its mitotic activity. In particular, they can cause a delay in mitosis, disrupt cytotomy, cause asymmetric and multipolar mitoses, and lead to the formation of multinucleated cells. Such violations prove the carcinogenic effect of chromium compounds.
The genotoxic effect of chromium compounds is manifested in its ability to increase the frequency of chromosomal aberrations, cause gene mutations such as “base pair substitution” or “reading frame shift,” and promote the formation of polyploid and aneuploid cells. (A.B. Bengaliev, 1986).
In addition to the mutagenic and carcinogenic effects, chromium compounds can cause denaturation of blood plasma proteins, disrupt enzymatic processes in the body, and cause changes in the respiratory system, gastrointestinal tract, liver, kidneys and nervous system. Promote the development of allergic processes, in particular dermatitis.
Acute poisoning with chromium compounds is manifested by dizziness, chills, nausea, vomiting, and abdominal pain.
With constant long-term contact with chromium compounds, bronchitis, bronchial asthma, dermatitis, and lung cancer develop. On the skin, most often on the lateral surfaces of the hands, in the lower part of the lower leg, peculiar chrome ulcers appear. The ulcers are superficial at first, slightly painful, have a “bird’s eye” appearance, later they deepen and become very painful.
Zinc
Zinc compounds are used in the smelting of lead-zinc ore, in the production of whitewash, in the smelting of aluminum, and in the galvanizing of utensils. Zinc oxide is used in the production of glass, ceramics, matches, cosmetics, and dental cement.
Routes of entry - mainly respiratory organs, excreted mainly through the intestines. Deposited in bones, hair, nails.
Zinc is a bioelement and is part of many enzymes and hormones (insulin). Its deficiency leads to atrophy of lymphoid organs and dysfunction of T-helper cells.
Entering the body in excess, zinc disrupts the permeability of cell membranes, accumulates in the cytoplasm and nucleus of the cell, is able to form complexes with phospholipids, amino acids and nucleic acids, and increase the activity of lysosomal enzymes. When zinc vapor is inhaled, the proteins of the mucous membranes and alveoli are denatured, the absorption of which leads to the development of “foundry fever”, the main manifestations of which are: the appearance of a sweetish taste in the mouth, thirst, a feeling of fatigue, chest pain, drowsiness, and dry cough. Then the temperature rises to 39-40 C, accompanied by chills and lasts for several hours and drops to normal numbers.
The painful condition usually lasts 2-4 days. In the blood test there is an increase in sugar, in the urine test the appearance of sugar, zinc, and copper.
As protection, it is recommended to use gas masks, special safety glasses and protective clothing at zinc production enterprises. Constant ventilation of the premises. Eating foods containing vitamin C.
Mechanisms of the body's defense against xenobiotics
Scientists have discovered that animals and humans have quite a few different defense mechanisms against xenobiotics. The main ones:
A system of barriers that prevent the penetration of xenobiotics into the internal environment of the body and protect especially important organs;
special transport mechanisms for removing xenobiotics from the body;
enzyme systems that convert xenobiotics into compounds that are less toxic and easier to remove from the body;
tissue depots where some xenobiotics can accumulate. A xenobiotic that enters the blood is, as a rule, transported to the most important organs - the central nervous system, endocrine glands, etc., in which histohematic barriers are located. Unfortunately, the histohematic barrier is not always insurmountable for xenobiotics. Moreover, some of them can damage the cells that form histohematic barriers, and they become easily permeable.
Transport systems that remove xenobiotics from the blood are found in many organs of mammals, including humans. The most powerful ones are found in the cells of the liver and kidney tubules.
The lipid membrane of these cells does not allow water-soluble xenobiotics to pass through, but this membrane contains a special carrier protein that recognizes the substance to be removed, forms a transport complex with it and carries it through the lipid layer from the internal environment. Then another carrier removes the substance from the cell into the external environment. In other words, all anthropogenic organic substances that form negatively charged ions (bases) in the internal environment are removed by one system, and those that form positively charged ions (acids) are removed by another. By 1983, more than 200 compounds of different chemical structures had been described that the organic acid transport system in the kidney can recognize and remove.
But, unfortunately, the systems for removing xenobiotics are not omnipotent. Some xenobiotics can destroy transport systems, for example, synthetic penicillin antibiotics - cephaloridines - have this effect, for this reason they are not used in medicine.
The next defense mechanism is enzyme systems that convert xenobiotics into less toxic and easier to remove compounds. For this, enzymes are used that catalyze either the breaking of any chemical bond in a xenobiotic molecule, or, conversely, its combination with molecules of other substances. Most often, the result is an organic acid that is easily removed from the body.
The most powerful enzyme systems are found in liver cells. Hepatocytes can even neutralize dangerous substances such as polycyclic aromatic hydrocarbons that can cause cancer. But sometimes, as a result of the work of these enzyme systems, products are formed that are much more poisonous and dangerous than the original xenobiotic.
Depot for xenobiotics. Some of them selectively accumulate in certain tissues and remain there for a long time; in these cases they talk about xenobiotic deposition. Thus, chlorinated hydrocarbons are highly soluble in fats and therefore selectively accumulate in the adipose tissue of animals and humans. One of these compounds, DDT, is still found in the adipose tissue of humans and animals, although its use in most countries of the world was banned 20 years ago. Tetracycline compounds are similar to calcium, and therefore are selectively deposited in growing bone tissue, etc.
Main literature
1. Shilov I.A. Ecology. – M.: Higher School, 1998.
2. Korobkin V.I., Peredelsky L.V. Ecology. – Rostov n/a: Phoenix Publishing House 2000.-576 p.
3. Korolev A.A. Medical ecology. – M.: “Academy” 2003. – 192 p.
4. Samykina L.N., Fedoseikina I.V., Bogdanova R.A., Dudina A.I., Kulikova L.N., Samykina E.V. Medical problems of ensuring quality of life - Samara: IPK LLC Sodruzhestvo, 2007. – 72 p.
Additional literature.
1. Agadzhanyan N.A., Volozhin A.I., Evstafieva E.V. Human ecology and survival concept. - M.: GOU VUNMC Ministry of Health of the Russian Federation, 2001.
2.Alekseev S.V., Yanuschyants O.I., Hygienic problem of childhood ecology in modern conditions. Environmental safety of cities: Abstracts. report scientific – practical conf. – St.-Pb, 1993.
3. Burlakova T. I., Samarin S. A., Stepanov N. A. The role of environmental factors in cancer incidence in the population of an industrial city. Hygienic problems of protecting public health. Conference materials. Samara., 2000.
4. Buklesheva M. S., Gorbatova I. N. Some patterns of the formation of morbidity among children in the area of a large petrochemical complex./Clinical and hygienic aspects of the prevention of occupational diseases at enterprises in the cities of the Middle Volga region: collection of scientific works. tr. MNIIG im. F. F. Erisman. – M., 1986.
5. Galkin R. A., Makovetskaya G. A., Stukalova T. I. et al. Problems of health of children in technogenic provinces./ Environment and health: Abstracts. report scientific – practical Conf. - Kazan, 1996.
6. Doblo A. D., Logashova N. B. Ecological and hygienic aspects of water supply to the region./Hygienic problems of protecting public health. Conference materials / Samara, 2001.
7. Zhukova V.V., Timokhin D.I. Hygienic problems of maintaining the health of the population of large cities. / Hygiene at the turn of the 21st century: Conference proceedings. Voronezh. – 2000.
8. Makovetskaya D. A., Gasilina E. S., Kaganova T. I. Aggressive factors and children's health. / Materials of the 6th International Congress “Ecology and Human Health”. Samara, 1999.
9. Potapov A. I., Yastrebov G. G. Tactics and strategies for complex hygienic research. // Hygienic problems of public health protection. Conference materials. Samara, 2000.
10. Sukacheva I. F., Kudrina N. V., Matyunina I. O. Ecological and hygienic situation of the Saratov reservoir within the city of Samara. / Hygienic problems of public health. Conference materials. / Samara, 2001.
11. Spiridonov A. M., Sergeeva N. M. On the state of the environment and the health of the population of the Samara region // Ecology and human health: Sat. scientific tr./ - Samara.
- Introduction
- Foreign xenobiotic compounds
- How does the body protect itself from xenobiotics?
- Antioxidants
4. Conclusion
Life Safety Teacher
Kovalev Alexander Prokofievich
Secondary school No. 2
Mozdok
A person lives surrounded by a variety of chemical substances, many of which belong to the group xenobiotics - foreign compounds.
Foreign connection- this is a substance that the body cannot use either to produce energy or to build any of its parts.
Foreign chemicals are poisonous or poisonous and have different origins.
Many of them are natural, but more than 7 million substances are created by man artificially; pesticides, household chemicals, medicines, industrial waste.
Many substances poison the planet - both organic and inorganic, 12 metals: beryllium, aluminum, chromium, selenium, silver, cadmium, tin, antimony, barium, mercury, thallium, lead - are toxic in all their compounds.
Three metals - lead, cadmium, and mercury - pose a particular threat to human life and health.
Each of the new chemicals can cause poisoning or chemical illness.
Toxins that enter the human body with water, air, or food can cause chemical trauma, which is always accompanied by mental damage : This is how nerve cells, the most vulnerable in the body, react to harmful substances.
Toxins can also cause more serious consequences - fatal poisoning. , and in some cases their effect will manifest itself years later in the form of certain diseases.
The cause of chemical poisoning can be many substances that we encounter in everyday life, for example: medications, if you exceed the dosage prescribed by the doctor, use drugs that have expired.
Another source: household chemicals: paints, varnishes, glue, washing powders, bleaches, stain removers, insect repellents.
In our country, they are responsible for more than a million cases of poisoning per year.
Today, more than 400 health hazards have been found in tobacco smoke.
First of all, this is radioactive polonium-210 and carcinogenic resins that cause cancer of most internal organs.
Besides, The tobacco plant accumulates cadmium salts from the soil to the greatest extent.
An aerosol of cadmium oxide enters the alveoli of the lungs with tobacco smoke and, together with the substances mentioned above, contributes to the development of lung cancer.
The absorption (absorption into the blood) of cadmium from the air is 80%.
For this reason, the cadmium content in the body of passive smokers is only slightly less than that of active smokers.
In addition to the substances mentioned above, tobacco smoke contains such well-known poisons as hydrocyanic acid, arsenic, carbon monoxide, which irreversibly bind to hemoglobin in the blood.
According to WHO estimates Smokers lose an average of 22 years of normal life.
The human and animal bodies have various defense mechanisms against xenonobiotics. The main ones:
1. These are systems of barriers that prevent the penetration of xenobiotics into the internal environment of the body, as well as protecting especially important organs (the brain, etc.) from those “strangers” that have nevertheless broken into the body.
2. These are special transport mechanisms for removing xenobiotics from the body. The most powerful of them is located in the kidneys
3. These are enzyme systems, the main ones of which are located in the liver and convert xenobiotics into compounds that are less toxic and easier to remove from the body.
4. These are tissue depots where some xenobiotics can accumulate, as if under arrest.
Barriers are the skin, epithelium lining the inner surface of the gastrointestinal tract and respiratory tract. These barriers are formed by single- or multi-layered layers of cells.
However, some substances can overcome these barriers.
If xenobiotics break into the blood, then they will be met by histohematic barriers located between the tissue and the blood.
But histohematic barriers are not always insurmountable for xenobiotics - after all, sleeping pills and some drugs act on nerve cells, which means they pass the barrier.
Some xenobiotics can damage the cells that form histohematic barriers, making them easily penetrated.
Transport systems are found in many organs. The most powerful ones are found in liver cells and kidney tubules.
In organs protected by the histohematic barrier, there are special formations that pump xenobiotics into the blood from tissue fluid
Enzyme systems convert xenobiotics into less toxic compounds that are easier to remove from the body.
To do this, enzymes are used that catalyze either the breaking of any chemical bond in the xenobiotic molecule, or, conversely, its connection with molecules of other substances.
Most often, the result is an organic acid that is easily removed from the body.
The most powerful enzyme systems are found in liver cells.
The xenobiotic depot is a place of selective accumulation of certain harmful substances.
Throughout the evolution of animals and humans, the gastrointestinal tract remained the main gateway for foreign substances to enter the body. Appropriate mechanisms for neutralizing xenobiotics penetrating from the intestines into the blood have also been formed: The liver has “taken over” the protective function
This powerful “chemical plant” ensured the preservation of the constancy of the body’s internal environment.
Now the situation has changed radically due to significant and varied environmental pollution.
For this reason, the human body is much more sensitive to the penetration of toxic substances into it both through the lungs and through the gastrointestinal tract.
The penetration of various harmful substances of increased concentration through the respiratory organs, which are less protected than the gastrointestinal tract, has led to a significant change in the state of the body these days.
Pathological hypersensitivity of the body has developed.
Hereditary defects are accumulating at a noticeable pace.
Chronic bronchitis and previously rare forms of pulmonary pathology, such as allergic inflammation of the alveoli (poultry farmer's disease, tobacco grower's disease, "farmer's lung", etc.), have become widespread.
The number of patients with bronchial asthma, the most severe manifestation of allergies, has increased.
Of particular concern is the increase in the number of patients with lung cancer.
Alcoholic drinks have been known for a long time. It is assumed that drinking alcohol was timed by our ancestors to coincide with such events as the full moon festival, a successful hunt, and symbolized mental kinship, “unity of blood.”
For a long time, people did not cross the dangerous line of drinking alcohol, but today alcoholism has become one of the most serious problems.
Antioxidants are substances that prevent oxidation or reactions that are activated by oxygen, peroxides, radicals , that is, they protect cell membranes.
Most vitamins are antioxidants. Since the load on the body with xenobiotics has increased sharply over the past decades, the consumption of vitamins and other antioxidants has increased sharply, and therefore the amount that comes with the usual diet is increasingly insufficient.
To remove many chemicals and heavy metals from the body, it is advisable to take sorbents: chitosan, fiber, pectins.
Think before you inject yourself with xenobiotics, including those called drugs.
Weigh the yin: yang, benefit: risk of complications.
Remember! To prolong life, it is enough not to shorten it!
No matter how perfect medicine is, it cannot rid everyone of all diseases. A person is the creator of his own health, for which he must fight.
From an early age it is necessary to lead an active lifestyle, toughen up, engage in physical education and sports, observe the rules of personal hygiene - in a word, achieve true harmony of health through reasonable means.
A healthy lifestyle is a way of life based on the principles of morality, rationally organized, active, working, hardening and, at the same time, protecting from the adverse effects of the environment, allowing one to maintain moral, mental and physical health until old age.
Homework § 3.1 p.18-24
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Xenobiotics pollute all natural environments - air, water bodies, soil and flora. Industrial waste and other environmental pollutants have the ability to quickly spread in air and water, becoming part of the natural cycle. These toxic compounds accumulate in water bodies and soil, sometimes in places far removed from sources of contamination, facilitated by wind, rain, snow, as well as the migration of pollutants by water (sea, rivers, lakes). From the soil they enter plants and animals.
Soil occupies a central place in the cycle of xenobiotics occurring in the biosphere. It is in constant interaction with other ecological systems, such as the atmosphere, hydrosphere, flora, and is an important link in the entry of various components, including toxic ones, into the human body. This happens primarily through food. All living beings need food as a source of energy, building materials and nutrients that ensure the vital functions of the body. However, if it contains not only useful but also harmful substances, it becomes dangerous. Xenobiotics cause diseases and death of plants and animals. Xenobiotics that are resistant to the environment and capable of accumulating in it are especially dangerous.
The prevalence of xenobiotics in the environment depends on climatic and meteorological conditions and the nature of water bodies. Thus, increased air humidity, wind direction, and precipitation (rain, snow) contribute to the prevalence and loss of xenobiotics. Freshwater bodies, seas and oceans differ in the degree of accumulation of xenobiotics. The type of soil, different plants and their components also differ in the degree of absorption and retention of xenobiotics. And different animals have different sensitivity to xenobiotics. The degree of accumulation of xenobiotics in the body of animals is determined by the persistence of these foreign substances.
Thus, Canadian researchers showed that the water of Lake Michigan contained only 0.001 mg of the pesticide DDT per liter, while shrimp meat contained 0.4 mg/l, fish fat - 3.5 mg/l, and seagull fat who ate fish from this lake - 100 mg/l. Consequently, at each subsequent link in the food chain there is a gradual increase in the concentration of the persistent pesticide DDT, and the lowest content of this substance was observed in the lake water. Therefore, it is not surprising that organochlorine pesticides are found not only in the fat of marine fish and farm animals, but even in penguins living in Antarctica.
A person must always remember that his activities at one point on the planet can cause unexpected consequences at another point. For example, the petrel seems to live on uninhabited rocks in the Atlantic Ocean and feeds exclusively on fish. However, it is becoming an endangered species due to DDT used on land, which accumulates in marine food chains. Another example would be polar ice, which contains significant residual amounts of DDT carried by precipitation.
Properties of xenobiotics coming from the external environment into the human body:
- the ability of xenobiotics to spread in our environment far beyond the boundaries of their original location (rivers, winds, rain, snow, etc.);
- environmental pollution is very persistent;
- Despite the wide differences in chemical structure, xenobiotics have certain common physical properties that increase their potential danger to humans;
- Combinations of various xenobiotics are especially dangerous for human health;
- xenobiotics are characterized by a low intensity of metabolism and removal, as a result of which they accumulate in the tissues of plants and animals;
- the toxicity of xenobiotics for higher mammals is usually higher than for animal species of lower phylogenetic order;
- the ability of xenobiotics to accumulate in food products;
- Xenobiotics reduce the nutritional value of foods.
During evolution on Earth, relationships developed in such a way that some organisms served as food for others and thus stable food chains were established. As a result, humans have become the main endpoint of numerous food pathways and can be included in these food chains at almost any level. And this is not surprising, since life from its inception was formed as a chain process. The prosperity of any organism is largely determined by its position in the food chain, and this is ensured by the effectiveness of interactions not only with previous, but also with subsequent members of the food chain. In other words, a significant role is played not only by the source of nutrition and its effective absorption, but also by the consumption of a given member of the ecological system by others.
Migration routes, i.e. The food routes through which nutrients move are diverse, including short and long. An example of a long food chain: water bodies - soil - plants - animals - food - humans. An example of a short food chain: reservoirs - aquatic organisms - fish - humans.
Organic substances formed in nature migrate through food chains in various ecological systems (atmospheric air, water bodies, soil) and enter the human body in the form of food products of plant and animal origin. However, food contains not only our friends, but also enemies, since at the same time numerous non-food, foreign substances, generated by the chemicalization of industry and agriculture and which are toxic to humans and other living beings, move along the food chain. Therefore, it is no coincidence that many scientists talk about poisons in our food. Recently, many scientists are also talking about protecting the internal environment of the human body.
Academician Pokrovsky says: “We are deeply convinced that an important integral criterion for food protection measures aimed at preventing diseases should be indicators of the chemical purity of the internal environment of the human body, with freedom from foreign, especially persistent substances. It should be recognized that the accumulation of any persistent foreign substance in the internal environment of the body is extremely undesirable, and in some cases dangerous.” This concept provides for completely obvious measures aimed at reducing the levels of pollution of all environmental objects, including food, by toxic substances. Thus, the cleanliness of the environment is a necessary prerequisite for the cleanliness of the internal environment of the human body.
Xenobiotics have a negative effect on nutrients (proteins, carbohydrates, fats, vitamins, mineral salts), thereby reducing the nutritional value of food products.
It should be borne in mind that contamination of food products with xenobiotics is possible not only during their receipt, but also during storage, processing, transportation and sale to the public. Environmental pollutants are quite stable with a tendency to spread, accumulate in food chains, and are capable of undergoing biotransformation with increasing toxicity. The severity of the effects caused varies widely depending on the degree and duration of exposure to xenobiotics. A number of xenobiotics can accumulate in the human body and, therefore, have a long-term harmful effect.
The negative effect of xenobiotics on the human body depends on their physicochemical properties, concentration, duration of exposure, ability to be deposited in the body and selectively influence certain tissues and organs. Consequently, many xenobiotics cause specific damage to various organs. Unfavorable environmental factors provoke or cause a state of stress in a large part of the population with subsequent metabolic disorders. The leading role of xenobiotics in the development of allergic conditions is also undoubted.
As a result of the accumulation of xenobiotics in the human body, the functions of internal organs are disrupted and various painful conditions develop, including serious illnesses with death or disability. Among these diseases, which can be acute or chronic, the possibility of developing malignant tumors and leukemia - blood cancer - is of particular concern. The diabolical samosa lies precisely in the insidiousness of food chains, in particular in the microscopic nature of food with a constant supply of xenobiotics. As a result, severe long-term consequences develop, in particular, deformed, non-viable offspring.
The role of soil as a central place in the cycle of substances has already been noted. This is the environment where most of the elements of the biosphere interact: water and air, climatic and physicochemical factors, and, finally, living organisms involved in the formation of soil. It is she who plays the leading role in creating food chains.
Thus, the food tract is the main route for the migration of substances harmful to humans, i.e. Xenobiotics enter the body mainly with food (70% of all those regularly entering the body, only 20% - with air and 10% - with water).
All food products contain components coming from air, water and soil as their primary sources. Depending on the nature of the food product, the path of transformation of these starting substances can be more or less long, straight or tortuous, and since environmental pollution is associated with a strong tendency for the distribution and accumulation of xenobiotics in food chains (pathways), as well as the ability to undergo transformation with increasing toxicity, the severity of the consequences they cause depends on the degree of their toxicity (or persistence) and the duration of exposure. The insidiousness of the penetration of xenobiotics into food chains is that a person eats constantly, which means that even in small quantities, harmful substances constantly enter his body. As already noted, migration routes, i.e. food paths (chains) of nutrients, beneficial and harmful to humans, are diverse.
Sources of environmental pollution by xenobiotics
|
Sources of pollution |
Xenobiotic |
Most contaminated product |
|
Electrical industry products |
Polychlorinated biphenols |
Fish, human milk |
|
Impurities in polychlorinated biphenols |
Dioxins |
Fish, cow's milk, beef fat |
|
Fungicides, industrial by-products |
Hexachlorobenzene |
Animal fats, dairy products |
|
Pesticide production |
Fish, human milk |
|
|
Pesticides |
Halogenated hydrocarbons |
Fish, human milk |
|
Production of chlorine and sodium hydroxide, communications processing equipment |
Alkyl mercury compounds | |
|
Automotive exhaust gases, coal combustion products |
Cereals, vegetables, fish, acidic foods |
|
|
Sediment sludge, products of metallurgical processes (smelting) |
Cereals, vegetables, meat products |
|
|
Products metallurgical processes |
Milk, vegetables, fruits |
|
|
Canning industry |
Canned foods |
Does the human body have the ability to neutralize to some extent the harmful effects of xenobiotics?
The answer may be positive, since the human body has certain defense mechanisms that make it possible to neutralize the pathogenic effects of xenobiotics.
These mechanisms include:
- a set of processes by which these foreign substances are removed from the body through natural routes of elimination (exhaled air, bile, intestines, kidneys);
- active neutralization of xenobiotics in the liver;
- transformation of foreign substances into less active chemical compounds;
- protective role of the body's immune system.
Lisovsky V.A., Evseev S.P., Golofeevsky V.Yu., Mironenko A.N.
To maintain homeostasis, biological objects in the process of evolution have developed special systems and mechanisms of biochemical detoxification. The mechanisms of protection against the effects of xenobiotics may be different in different types of biological objects. However, the body's defense systems are the same, and they are classified according to their purpose and mechanisms of action.
By purpose they are distinguished:
Systems serving to limit the toxic effects of xenobiotics (barriers, tissue depots);
Systems that serve to eliminate the toxic effects of xenobiotics (transport and enzyme systems).
The mechanisms of action of defense systems depend on the routes of penetration of xenobiotics into the body.
Barriers. There are two barrier defense systems in the animal and human body:
Barriers that prevent xenobiotics from entering the internal environment of the body;
Barriers that protect particularly important organs (brain, central nervous system, endocrine glands, etc.).
Role barriers that protect the internal environment of the body, performed by the skin and epithelium of the inner surface of the gastrointestinal tract and respiratory tract. The skin of animals and humans makes up more than a quarter of body weight (for the average person up to 20 kg). The skin consists of three main layers: the epidermis (the top layer of the skin), the dermis (the inner layer, or the skin itself) and subcutaneous fat (Fig. 9). The upper layer of the skin has a complex structure and consists of the horny, transparent, granular, spinous and germinal layers. The barrier function is performed by the deep part of the stratum corneum and transparent layers. The main structural component of barriers is structural proteins. The horny substance is formed by a-keratins (from gr. keras horn), containing in the molecule the remains of all 20 natural amino acids.
The transparent layer is formed by single and multilayer plates of cells. Each cell is surrounded by a thin film of fat - a lipid membrane, impermeable to water-soluble substances. However, substances that are highly soluble in lipids can overcome this barrier. The main structural component of the lipid membrane is glycerolipid.
Lipids(from gr. lipos fat) are fat-like substances that are part of all living cells. According to their chemical structure, there are three main groups of lipids:
Fatty acids and products of their enzymatic oxidation;
Glycerolipids (contain a glycerol residue in the molecule);
Lipids that do not contain a glycerol residue in the molecule (except for the first).
The ability of skin barriers to protect the internal environment of the body from the penetration of xenobiotics into it depends on:
Nature of xenobiotics (composition, chemical properties, reactivity, hydrophilicity, etc.) Hydrophilic substances dissolve in aqueous tissue solutions, and fat-soluble substances dissolve in lipids. Skin barriers protect the internal environment of the body from the ingress of water-soluble substances and from the effects of aqueous solutions of acids, hydroxides, and salts. However, organic solvents and substances that dissolve in them penetrate through these barriers. Substances that are diphilic in nature are especially dangerous;
The size of xenobiotic molecules (particles) determines the possibility of their penetration into the internal environment of the body through the skin and skin ducts of the sweat and sebaceous glands. The main route is absorption through the skin. Large molecules (protein) remain on the surface of the skin without penetrating deep, and small particles can penetrate inside.;
Age of the body Skin permeability to water does not change with age.
In cases where xenobiotics penetrate the stratum corneum and lipid membranes, the epithelium of the inner surface of the gastrointestinal tract and respiratory tract and enter the bloodstream, the function of barriers protecting especially important organs is performed by histohematic barriers(from gr. histos tissue + haima blood), located between tissue and blood. Some xenobiotics can damage cells that form histohematic barriers. Histohematic barriers are most damaged by transition metal ions that form organic complexes with proteins and amino acids (cadmium, zinc, chromium, mercury ions).
To maintain the vital functions of the body, old barrier cells are replaced with new ones. Red blood cells are completely renewed monthly, the horny substance is removed from the skin daily (up to 6 g), and the skin is completely renewed within a month. The epithelium of the inner surface of the gastrointestinal tract and respiratory tract is renewed weekly.
Depot for xenobiotics. Some xenobiotics accumulate in certain tissues of the body and can persist there for a long time. Tissue depots, collecting xenobiotics in one tissue, protect the internal environment of the body from it and help maintain homeostasis. However, if a xenobiotic lingers in the depot for a long time and its concentration increases significantly over time, then its toxic effect will turn from chronic to acute.
The ability of xenobiotics to accumulate in certain tissues or organs is determined by their composition, structure and physicochemical properties.
Non-electrolytes, metabolically relatively inert and having good lipoid solubility, accumulate in all organs and tissues. Moreover, in the first phase of the poison entering the body, the determining factor will be the blood supply to the organ, which limits the achievement of dynamic equilibrium blood tissue. However, in the future, the main factor influencing the distribution of poison is the sorption capacity of the organ (static equilibrium). For lipid-soluble substances, adipose tissue and organs rich in lipids (bone marrow, etc.) have the greatest capacity. For many lipid-soluble substances, adipose tissue is the main depot, retaining the poison both in larger quantities and for a longer time than other tissues and organs. In this case, the duration of preservation of poisons in the fat depot is determined by their physicochemical properties. For example, desaturation of adipose tissue after poisoning of animals with benzene occurs within 30-48 hours, and with the insecticide DDT - over many months.
For the distribution of metal ions in the body, in contrast to organic non-electrolytes, no general patterns have been identified that connect the physicochemical properties of the latter with their distribution. However, in general, metal ions tend to accumulate most in the same tissues and organs where they are normally found in large quantities as trace elements. In addition, selective deposition of metal ions is found in tissues where there are polar groups capable of donating electrons and forming coordination bonds with metal atoms, and in organs with intense metabolism. For example, the thyroid gland absorbs manganese, cobalt, nickel, chromium, arsenic, rhenium; adrenal glands and pancreas – manganese, cobalt, chromium, zinc, nickel; pituitary gland – manganese, lead, molybdenum; the testes absorb cadmium and zinc.
The deposition of ions of most transition metals in the body is primarily due to their ability to form various organic complexes with proteins and amino acids. Ions of metals such as zinc, cadmium, cobalt, nickel, thallium, copper, tin, ruthenium, chromium, mercury are distributed evenly in the body. They are found during intoxication in all tissues. At the same time, some selectivity of their accumulation is observed. Selective deposition of mercury and cadmium in any form occurs in the kidneys, which is associated with the specific affinity of these metals for the SH group of kidney tissue. In the form of coarse colloids, some poorly soluble rare earth metals are selectively retained in organs such as the liver, spleen, and bone marrow, which are rich in reticuloendothelial cells. Bone tissue selectively accumulates ions of those metals whose inorganic compounds dissociate well in the body, as well as metal ions that form strong bonds with phosphorus and calcium. Such metals include lead, beryllium, barium, strontium, gallium, yttrium, zirconium, uranium, and thorium. In addition, lead, when inhaled for a long time, is also found in maximum quantities in the liver, kidneys, spleen and heart muscle.
The release of metal ions from the body obeys an exponential law. After the cessation of intake, their content in the body quickly normalizes. In many cases, the release proceeds unevenly, multiphase, and each phase has its own exponential curve. For example, most of the inhaled mercury vapor is removed from the body by the kidneys within a few hours, but the removal of its residual quantities is delayed for several days; the release of residual amounts of uranium lasts up to 900 hours, and the release of zinc lasts more than 150 days.
Transport systems. According to their purpose in the body of animals and humans, transport systems are divided into two groups. The first group includes transport systems that cleanse the internal environment of the entire body. The second group consists of transport systems that remove the xenobiotic from the most important one organ.
Transport systems of the first group are found in many organs, but the most powerful of them are in the cells of the liver and kidney tubules.
Food and other substances in the stomach are only partially digested. Most of the digestive process takes place in the small intestine. Digested food and small molecules and xenobiotic ions pass through the walls of the small intestine into the blood and enter the liver with the bloodstream. Undigested food and xenobiotic molecules or ions that do not pass through the walls of the small intestine are eliminated from the body.
In liver cells, a structural carrier protein identifies harmful substances and separates them from useful ones. Substances useful to the body (glucose, stored in the form of glycogen, and other carbohydrates, amino acids and fatty acids) are released into the blood for transfer to those cells whose vital activity they provide. A small portion of glucose and amino acid molecules are returned to the liver to be converted into proteins needed by the blood.
Ballast substances and some xenobiotics are transported by bile into the intestine and excreted from the body. Other xenobiotics undergo chemical transformations in the liver, making them less toxic and more soluble in water, easily excreted from the body.
In the process of removing xenobiotics and their transformation products from the body, the lungs, digestive organs, skin, and various glands play a certain role. The kidneys are of greatest importance. The function of the kidneys, which determines the elimination processes, is used in cases of poisoning by increasing urination to quickly remove toxic substances from the body. However, many xenobiotics (mercury, etc.) have a damaging effect on the kidneys. In addition, xenobiotic transformation products may be retained in the kidneys. For example, in case of ethylene glycol poisoning, during its oxidation, oxalic acid is formed in the body and calcium oxalate crystals precipitate in the kidney tubules, preventing urination.
Transport systems of the second group are found, for example, in the ventricles of the brain. They remove xenobiotics from cerebrospinal fluid(fluid that bathes the brain) into the blood.
The mechanism for the removal of xenobiotics by the transport systems of both groups is the same. Transport cells form a layer, one side of which borders on the internal environment, and the other on the external environment. The lipid membrane of the cells of this layer does not allow water-soluble xenobiotics to enter the internal environment of the cell. But this membrane contains a special transport protein - carrier protein, which identifies a harmful substance, forms a transport complex with it and carries it through the lipid layer from the internal environment to the external environment.
The bulk of xenobiotics are excreted by two transport systems: for organic acids and for organic bases.
The number of carrier protein molecules in the membrane is limited. At a high concentration of xenobiotics in the blood, all molecules of the transport protein in the membrane can be occupied, and then the transfer process becomes impossible. In addition, some xenobiotics damage or even kill transport cells.
Transport of metal ions is carried out mainly by blood in the form associated with protein fractions of blood. Red blood cells play a major role in the transport of many metal ions (for example, lead, chromium, arsenic).
Enzyme systems. In the processes of detoxification of xenobiotics that enter the bloodstream, the decisive role is played by enzyme systems that convert toxic xenobiotics into less toxic compounds that are more soluble in water and easier to remove from the body. Such chemical transformations occur under the influence of enzymes that catalyze the rupture of any chemical bond in a xenobiotic molecule or, conversely, the interaction of xenobiotic molecules with molecules of other substances.
The most powerful enzyme systems are found in liver cells. In most cases, liver enzyme systems neutralize xenobiotics that enter the blood flowing from the intestines and entering the liver, and prevent their entry into the general bloodstream. A typical example of the process of detoxification of xenobiotics by liver enzyme systems is the biochemical transformation in the body of benzene, which is poorly soluble in water, into pyrocatechol, which is highly soluble in water and easily excreted from the body.
The biochemical transformation of benzene in the body occurs in three directions: oxidation (hydroxylation) of benzene into aromatic alcohols, the formation of conjugates and the complete destruction of its molecule (rupture of the aromatic ring).
Another example of the process of detoxification of xenobiotics by liver enzyme systems is the oxidation of toxic sulfite to sulfate:
2SO 3 2– (aq) + O 2 (aq) 2SO 4 2– (aq)
The enzyme that catalyzes this reaction contains a molybdenum ion. Without this trace element in liver cells, most food would be toxic to humans and animals.
The ability of liver enzyme systems to neutralize xenobiotics contained in the bloodstream is limited. Since detoxification processes are associated with the consumption of substances that are essential for the life of cells, these processes can cause their deficiency in the body. As a result, there is a danger of developing secondary painful conditions due to a deficiency of necessary metabolites. For example, the detoxification of many xenobiotics depends on liver glycogen stores because they produce glucuronic acid. When large doses of xenobiotics enter the body, the neutralization of which is carried out through the formation of glucuronic acid (for example, benzene derivatives), the content of glycogen (the main easily mobilized reserve of carbohydrates) decreases. However, there are substances that, under the influence of liver enzymes, are capable of splitting off glucuronic acid molecules and thereby helping to neutralize poisons. One of these substances is glycyrrhizin, which is part of the licorice root.
In addition, when xenobiotics enter the bloodstream in large doses, liver function can be suppressed. Overloading the liver with xenobiotics can also lead to their accumulation in the fatty tissues of the body and chronic poisoning.
