Synthesis of urea. Urea - what is it? Causes of increased or decreased urea in the blood. Analyzes Scheme for synthesis of urea
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What is urea?
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By itself, urea is not of serious importance to the body. It does not perform any functions in the blood or in the internal organs. This compound is necessary for the safe removal of nitrogen from the body.
Normally, the highest concentration of urea is observed in the blood and urine. Here it is determined by laboratory methods for medical reasons or during a preventive examination.
From the point of view of diagnostics, urea is an important indicator that can indicate a number of abnormalities in the body. The level of urea indirectly indicates the work of the kidneys and liver. When combined with other blood tests and urinalysis, this provides extremely valuable diagnostic information. Many treatment protocols and accepted standards are based on the results of a urea test.
How does biosynthesis occur? education) and hydrolysis ( decay) urea in the body?
The formation of urea occurs in the body in several stages. Most of them ( including the synthesis of urea itself) takes place in the liver. The breakdown of urea normally does not occur in the body or occurs in small quantities and has no diagnostic value.The process of formation of urea from proteins goes through the following stages:
- Proteins break down into simpler substances - amino acids containing nitrogen.
- The breakdown of amino acids leads to the formation of toxic nitrogen compounds that must be removed from the body. Most of these substances are excreted in the urine. Most of the nitrogen goes to the formation of urea, somewhat less - to the formation of creatinine, and a small part - to the formation of salts, which are also excreted in the urine.
- In the liver, urea is formed as a result of biochemical transformations ( ornithine cycle). From here it enters the bloodstream and circulates in the body for some time.
- As the blood passes through the kidneys, harmful substances are trapped and concentrated through the filtration process. The result of this filtration is secondary urine, which is excreted from the body during urination.
How is urea different from uric acid?
Urea and uric acid are two different substances found in the human body. Urea is a breakdown product of proteins, amino acids and a number of other compounds. It normally circulates in the blood small part) and is excreted in the urine. Uric acid is formed as a result of the breakdown of purine bases. This process takes place mainly in the brain, liver and blood. It aims to neutralize ammonia ( toxic nitrogen compound). Uric acid can be excreted from the body in small amounts with sweat and urine.If the accumulation of urea in the body does not in itself pose a serious danger ( it only indicates various diseases), then uric acid can accumulate in various tissues in the form of salts. The most serious pathology associated with uric acid metabolism disorders is gout.
What does the level of urea in the blood and urine show?
Normally, the concentration of urea in the blood and urine is affected by the work of the liver and kidneys. Thus, deviations of its concentration from the norm can be analyzed to diagnose various pathologies of these organs. For more complete information, the results of biochemical tests for other substances are also taken into account.In general terms, deviations in the level of urea can be interpreted as follows:
- Decrease in the level of urea in the blood. This deviation can occur during starvation and a diet poor in proteins. If there are no visible causes, various pathologies of the liver should be suspected. That is, in the body, the breakdown of proteins occurs in the usual manner, but for some reason the liver does not neutralize ammonia, transforming it into urea.
- An increase in the level of urea in the blood. A slight increase in combination with an increased level of urea in the urine can be considered a variant of the norm. In the body, there is an accelerated breakdown of proteins and, as a result, more urea is formed. If the concentration is increased several times, this usually indicates serious kidney disease. The blood is poorly filtered, and a significant part of the urea is retained in the body.
- Decrease in the level of urea in the urine. Normally, the kidneys excrete a relatively stable amount of urea per day. If the level of urea in the blood is increased, and in the urine it is lower, this indicates that the kidneys are not performing their functions well. The blood is filtered worse, and toxic substances can linger in the body. This deviation is most often found in various kidney diseases, but it can also indicate a number of metabolic disorders or some systemic pathologies ( for example, many autoimmune diseases can damage the filtering apparatus of the kidneys).
- An increase in the level of urea in the urine. This deviation is almost always associated with an increased level of urea in the blood. Enhanced protein breakdown for various reasons) leads to accelerated urea formation. Healthy kidneys usually cope with this problem and begin to excrete this substance in the urine more quickly.
What organs influence the formation of urea ( liver, kidneys, etc.)?
Urea, like many other chemicals in the human body, is formed in the liver. It is this organ that combines many functions, including the neutralization of some metabolic products. During normal liver function, toxic nitrogenous compounds are converted into urea and released into the blood.The second organ that affects the level of urea is the kidneys. This is a kind of filtration apparatus of the body, which purifies the blood of unnecessary and harmful substances. During normal kidney function, most of the urea is excreted from the body in the urine.
Other organs can indirectly influence the rate of formation and excretion of urea from the body. For example, the thyroid gland, producing too many hormones ( hyperthyroidism), stimulates the breakdown of proteins, which is why the liver has to quickly convert their decay products into urea. However, it is the liver and kidneys that directly affect the level of this substance in the blood.
What is the role and function of urea in the human body?
Urea does not perform any functions in the human body. It is an excipient, a breakdown product of proteins and amino acids, which can be easily excreted from the body. This is a kind of transport form for substances that are no longer needed. In addition, the formation of urea by the liver saves the body from the accumulation of toxic substances ( ammonia, etc.). Thus, the main role of urea in the body is the excretion of nitrogen metabolic products.How is urea and other metabolic products excreted from the body?
Urea is the main product of nitrogen metabolism ( proteins, amino acids, etc.). Normally, it is excreted from the body in several stages. Urea synthesized in the liver circulates in the blood for some time, and then enters the kidneys. Here it passes the filtration membrane and lingers in the composition of the primary urine. A number of substances useful for the body and most of the water are then absorbed back in the process of reabsorption ( in the renal tubules). A small part of the urea can also return to the bloodstream. However, most of it enters the renal pelvis as part of the secondary urine.With urine, urea passes through the ureters to the bladder, from where it is excreted from the body during urination. At each stage of urea excretion, various violations can occur that will lead to the retention of this substance in the body.
There are the following types of azotemia ( retention of urea and other nitrogen compounds):
- Adrenal. This type is caused by excessive formation of urea and other products of nitrogen metabolism. At the same time, the kidneys function normally, but they do not have time to remove all these substances from the body in a short time.
- Renal. In this case, urea is delayed due to the fact that the kidneys no longer filter the blood normally. With this type of azotemia, the level of urea can reach the highest values ( 100 mmol/l and more).
- Subrenal. This type of azotemia is rare and is associated with difficulty in excreting secondary urine. That is, urea has already been filtered from the blood in the kidneys, but due to mechanical obstructions in the renal pelvis, ureter, or lower genitourinary system, urine is not excreted normally. Some of the substances from it are absorbed back into the blood during a delay.
Causes of high and low urea levels
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The following mechanisms and factors can influence the increase in the level of urea in the blood:
- The concentration of proteins in the blood ( increased formation of urea). The level of proteins in the blood also affects, in part, the rate of their breakdown. The more protein breaks down, the more urea is formed in the liver, and the more it enters the bloodstream. For example, after operations, injuries or burns, a large number of cells die, and many decay products enter the bloodstream ( including proteins).
- Diet. A significant amount of protein enters the body with food. The richer the diet in proteins, the more proteins will be in the blood. However, this mechanism does not affect the concentration of urea in the blood or urine as much.
- The volume of circulating blood. As a result of physiological or pathological processes, the volume of blood in the human body can change. For example, massive bleeding, diarrhea, or prolonged fever reduce blood volume, while multiple IVs, increased fluid intake, or certain diseases increase it. A change in circulating blood volume affects the concentration of urea in the blood or urine due to its dilution, but its amount ( like substances) does not change.
- Liver condition. Urea is formed in the liver from protein breakdown products ( nitrogen compounds) during normal operation of this organ. Various liver diseases lead to the fact that its cells perform their functions worse. Because of this, the formation of urea may decrease, and other toxic substances will accumulate in the blood.
- kidney condition ( excretion of urea from the body). Urea, which is formed in the liver, circulates in the blood for some time, after which it is excreted by the kidneys in the urine. In a number of kidney diseases, the filtration process may be slower, and the level of urea in the blood will increase, even if it is formed at a normal rate and in a normal amount.
- Other factors. Many different enzymes, cells and their receptors are responsible for the metabolism of proteins, the formation of urea and its excretion from the body. There are many different diseases usually rare), which affect certain links in the chain of protein metabolism. Some of these diseases are genetic and difficult to treat.
Why does urea increase in a child?
An increase in the level of urea in a child may be associated with various pathologies. Serious kidney disease in children is relatively rare. The most common cause is various infectious diseases of childhood and adulthood ( intestinal, respiratory, etc.). In most cases, they are accompanied by fever, which affects the concentration of urea in the blood.In addition to infectious diseases, the following reasons for an increase in the level of urea in the blood are possible:
- food poisoning with profuse vomiting or diarrhea;
- injury ( especially burns);
- prolonged fasting;
- diabetes ( in children, usually congenital);
- a number of diseases of the endocrine glands ( endocrine pathologies).
It is usually not possible to independently determine the cause of an increase in urea in children. The results of the analysis should be interpreted by the pediatrician, who will assess the general condition of the child and take into account the results of other laboratory tests.
Reduced urea in children is usually found in hepatitis ( inflammation of the liver tissue) of various origins.
Why does urea increase or decrease during pregnancy?
Normally, during pregnancy, the content of urea in the blood decreases. This is due to the fact that the woman's body intensively synthesizes new proteins necessary for a growing organism. The breakdown of proteins slows down, and less urea is formed. With normal kidney function, it is quickly excreted from the body with urine and does not linger in the blood.An increase in the level of urea during pregnancy most often indicates the development of any pathological processes. For example, in nephropathy of pregnancy, renal filtration deteriorates, and urea begins to accumulate in the blood ( while it will be lowered in the urine). In addition, pregnancy can provoke an exacerbation of various chronic pathologies, metabolic disorders or hormonal disruptions are possible, which often affect the functioning of the kidneys. If during pregnancy a biochemical analysis revealed an increased concentration of urea in the blood, a specialist consultation and additional examinations are required.
Does the consumption of water and other fluids affect the concentration of urea?
Excessive or insufficient fluid intake has some effect on the results of almost all laboratory tests. The fact is that increased drinking of water, one way or another, leads to an increase in the volume of circulating blood. Thus, the concentration of substances will be reduced. For the analysis, a standard volume of blood is taken, but a significant part of it will be water. The consumption of a large amount of liquid will lead to a slight decrease in the concentration of urea, and dehydration will lead to an increase. These deviations will not affect the state of health, since the amount of urea in both cases is the same. It disintegrates and outputs normally. Only the volume of blood in which it is dissolved changes.Does diet affect plasma, serum, blood, and urine urea levels?
The diet and foods consumed can partly affect the concentration of urea in the blood and urine. A diet high in protein causes this protein to begin to break down. Urea, on the other hand, is a product of this breakdown, and more of it is formed. A vegetarian diet with reduced protein intake reduces urea levels. However, nutrition usually leads to minor deviations from the norm. For example, if a person eats a lot of meat for several days before donating blood for analysis, the urea concentration will be at the upper limit of normal or slightly increased. Significant deviations ( exceeding the norm by 2 - 3 times or more) appear only in the presence of pathological processes.Is urea found in milk and other foods?
Urea is one of the waste products of living organisms, but normally it is excreted naturally in the urine. This substance cannot enter food. If contamination of the product occurs, it does not affect its nutritional value and does not pose a danger to the body.The level of urea in the blood can be affected by foods containing a lot of proteins and other nitrogenous substances. That is, after consuming these products, more urea is formed in the body, and its concentration in the blood increases.
A significant amount of protein is found in the following foods:
- meat;
- Fish and seafood ( shellfish, canned fish, some algae, etc.);
- cheeses;
- cottage cheese, etc.
Does being overweight affect urea levels?
There is no direct relationship between overweight and the concentration of urea in the blood or urine. An excess amount of urea can be observed in cases where excess weight is caused by a number of diseases. For example, in some patients with diabetes, metabolism is disturbed. This can affect the metabolism of proteins, and the functioning of the kidneys, and the gradual accumulation of excess weight. There are other pathologies that cause both excess weight and an increase in the level of urea. In each case, you should contact a specialist who will determine the root cause of these violations.What diseases cause an increase in the level of urea?
There are many different pathologies that can lead to an increase in the level of urea in the blood and urine. Most often, these are kidney diseases or various metabolic disorders. The most pronounced rise is observed in pathologies that cause renal failure.The level of urea in the blood can be increased in the following diseases and pathological conditions:
- acute and chronic renal failure;
- some tumors of the genitourinary system;
- stones in the kidneys ( nephrolithiasis);
- high or low blood pressure ( including some heart diseases);
- bleeding;
- a number of inflammatory diseases of the kidneys;
- a number of serious infectious diseases ( tropical hemorrhagic fevers, etc.);
- burns ( especially large area);
- wounds with damage to a large amount of tissue;
- poisoning with some toxins ( mercury, chloroform, phenol, etc.);
- severe dehydration;
- postoperative period;
- some oncological diseases;
- taking a number of pharmacological drugs ( sulfonamides, tetracycline, gentamicin - from antibiotics, as well as furosemide and lasix).
Urea is an important diagnostic criterion only for diseases of the liver and kidneys. In this case, according to its level, it is possible to draw indirect conclusions about the severity of the disease and choose the tactics of treatment ( e.g. kidney failure).
An increase in the level of urea in the urine most often appears simultaneously with its increase in the blood. The body tries to get rid of toxins in this way. However, there are a number of pathologies that increase the release of urea.
A high concentration of urea in the urine can be observed with the following diseases:
- some pernicious anemias;
- prolonged fever;
- taking thyroxine ( thyroid hormone);
- thyroid disease leading to thyrotoxicosis ( excessive secretion of thyroxine).
The norm of urea ( in men, women and children)
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There are the following normal limits for the concentration of urea in the blood at different ages:
- in newborns 1.4 - 4.3 mmol / l ( for children born before the due date, there are rules);
- in children under 3 years old, the norm is 1.8 - 6.4 mmol / l;
- in children under 10 years old - 2.0 - 6.8 mmol / l;
- in adolescents and adults - 2.5 - 8.3 mmol / l;
- in the elderly, approximately 3.5 - 9.3 mmol / l ( depends on the age and functional state of the kidneys, which deteriorates over time).
For the excretion of urea in the urine at different ages, there are the following normal limits:
- the first week of life - 2.5 - 33 mmol / day;
- 1 week - 1 month - 10 - 17 mmol / day;
- up to 1 year - 33 - 67 mmol / day;
- up to 2 years - 67 - 133 mmol / day;
- up to 8 years - 133 - 200 mmol / day;
- up to 15 years - 200 - 300 mmol / day;
- in adults - 333 - 587 mmol / day.
Why is the urea rate different in adults and children of different ages?
Normal levels of urea in the blood and urine vary depending on the age of the patient. This is due to the fact that the metabolism can proceed at different speeds. In a healthy child, it happens faster, as the body grows and develops. In old age, the metabolism slows down. This explains the different limits of the norm for patients of different ages.The most significant differences are observed in young children, since in the first years of life the body undergoes serious changes. In addition, the amount of protein consumed varies, and the volume of circulating blood gradually increases. All this affects the concentration of urea in the blood and urine, and, accordingly, the results of the tests. Different limits of the norm at different ages exist not only for urea, but also for most other substances in the blood and urine.
The concentration of urea in the blood
The concentration of urea in the blood depends on several factors. Firstly, this is affected by the breakdown of proteins in the body, since it is urea that is its final product. Secondly, an important role is played by the work of the liver, in which this substance is synthesized. Thirdly, the work of the kidneys is important, which normally remove urea from the blood. In a healthy body, where all processes proceed normally and all organs function well, the concentration of urea in the blood ranges from 2.5 to 8.32 mmol / l. The boundaries of the norm can be somewhat expanded in people of different ages and under certain physiological conditions. A significant increase in urea in the blood is usually observed in renal failure, when this substance is poorly excreted from the body.The concentration of urea in the urine
The main function of the kidneys is to filter the blood and remove harmful substances from the body through the urine. Normally, urea is formed in the liver, circulates in the blood for some time, and then leaves the body with urine. Thus, the main factor affecting the concentration of urea in the urine is the filtration of blood in the kidneys. Normally, in healthy people, urea excretion is 333 - 587 mmol / day ( or 20 - 35 g / day). Provided that the kidneys are working normally, there is a proportional relationship between the concentration of urea in the blood and in the urine. The more of this substance is formed, the more it will be excreted in the urine. Any deviations from this proportion can be interpreted as signs of certain disorders, the cause of which remains to be identified.It should be noted that the generally accepted criterion in this case is not so much the concentration of urea in the urine as its total volume, which is excreted per day. This indicator is more reliable, since more factors can influence the amount of daily urine ( for example, heavy sweating or fluid intake). Regardless of this, the total amount of urea excreted by the body per day should be within the normal range.
Urea analysis
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Urea testing is rarely performed in isolation, as it will not provide the information necessary for a full diagnosis. For preventive purposes, a complex biochemical analysis of blood and urine is prescribed ( it is recommended to do it every 1-2 years, if there are no additional indications).
Separately, urea and creatinine may be determined as directed by a physician in patients with renal or hepatic insufficiency.
This examination can be done in any clinical laboratory. You don't need a referral from your doctor to do this. The laboratory usually attaches a brief transcript to the results of the analysis ( whether the result is within the normal range for this patient). It should be noted that the concentration of urea in the blood and urine can change quite quickly. Therefore, the results of the analysis when visiting a doctor should be fresh. It is recommended to carry them out 1 - 3 days before visiting a specialist. It is best to first go through a consultation, during which the doctor will be able to suggest which laboratory tests ( besides urea) are needed for this patient.
How to take a urea test?
For an objective assessment of the level of urea in the blood and urine, you need to follow a number of simple recommendations. The fact is that a person’s lifestyle and nutrition can affect the results of a biochemical blood test. That is why preparation is necessary before donating blood or urine for analysis.When preparing for a biochemical analysis of blood and urine, the following rules must be observed:
- do not give the body a heavy load 24 hours before the study;
- follow a normal diet the day before donating blood or urine ( especially do not abuse meat, fish or confectionery);
- in the morning, immediately before donating blood, do not eat ( drink water or tea without sugar);
- avoid severe stress.
Blood chemistry
A biochemical blood test is one of the methods of laboratory diagnostics. Unlike a general blood test, biochemical reactions are used here to determine various indicators. Determination of the level of urea in the blood and urine is included in the biochemical blood test.In general, this diagnostic method provides information about the work of internal organs ( especially the liver and kidneys). The results of a biochemical blood test are best considered in combination, as this will give a more complete picture of the state of the body. That is why a separate analysis for urea is usually not prescribed. An isolated increase or decrease in the concentration of one substance will not be a sufficient argument for making a diagnosis. In parallel with the determination of urea, it is important to determine the level of creatinine, total protein and a number of other indicators ( which are also included in the biochemical blood test).
What are the reactions and methods for determining urea?
In laboratory diagnostics, there are various methods for determining the concentration of urea in the blood. In each laboratory, a particular method is preferred, but this practically does not affect the result of the analysis. For the patient, this may only affect the cost of the analysis.Determination of the level of urea in the blood and urine is possible using the following methods:
- Gasometric. As a result of a chemical reaction, urea is decomposed into simpler substances, one of which is carbon dioxide. Using a special apparatus, the volume of gas is measured, and then calculated by the formula, what was the initial amount of urea in the sample.
- Direct photometric. Urea also reacts with several reagents in this method. The reaction products are determined by their ability to absorb light waves of a certain wavelength. This method also requires special equipment. The main advantage is the small amount of blood or urine required for analysis.
- Enzymatic. In this case, the urea in the sample is decomposed with the help of special enzymes. The reaction products are determined by subsequent chemical reactions, and their amount is measured by titration. This method is more time-consuming, since the determination of the concentration of substances takes place in several stages.
Does a complete blood count show the concentration of urea?
A general blood test is aimed primarily at determining the cellular composition of the blood. In this analysis, a microscope is used, under which a laboratory assistant or doctor counts the number of certain cells. Urea is a molecule of a substance that cannot be seen under a microscope. To determine it, special chemical reactions are carried out. That is why the concentration of urea is not determined as part of a general blood test, but a biochemical analysis is carried out.What other substances need to be checked simultaneously with the analysis for urea ( residual nitrogen, bilirubin, total protein, urea to creatinine ratio)?
A biochemical blood test, in which an analysis is made for the content of urea, also includes the determination of a number of other substances. To correctly interpret the results of the analysis, it is often necessary to compare the concentration of various substances. This allows you to get a more complete picture of the work of internal organs.In parallel with the determination of urea, it is recommended to take an analysis for the following substances in the blood:
- residual nitrogen. Residual urea nitrogen is determined by a special formula. The initial data for this is the level of urea. From the point of view of diagnostics, the level of urea and the level of residual urea nitrogen reflect the same processes, therefore, one of these indicators is usually determined ( the second can be easily calculated, even if it is not listed in the test results).
- Bilirubin. Bilirubin is the result of the breakdown of hemoglobin. This substance is formed after the death of red blood cells in the course of several biochemical transformations. In the liver, bilirubin binds and is excreted from the body ( with bile). The level of bilirubin indirectly reflects the work of the liver, but there is no direct connection with the formation of urea. It just adds to the overall picture.
- total protein. Since urea is formed as a result of the breakdown of proteins, the determination of total protein is often necessary to obtain a reliable and complete picture of the disease. For example, if the total protein is greatly increased, then urea cannot be normal, since a significant part of the proteins breaks down, and more urea is formed. A normal level of urea in these cases will indicate problems with its formation.
- Creatinine Creatinine is a product of energy metabolism reactions in cells. In part, it is associated with the breakdown of proteins in the body. Like urea, creatinine indirectly reflects the efficiency of the kidneys.
What does the increase and increase in urea mean in the analysis ( decoding analysis for urea)?
Abnormalities in the analysis of urea are interpreted by comparing the results with other symptoms that the patient has. In itself, an increase in the level of urea in the blood most often indicates problems with the kidneys. It is this organ that is responsible for removing urea from the body. In this case, the excretion of urea in the urine decreases, and the patient may experience swelling and other symptoms of kidney failure. A low level of urea in the blood often indicates problems with the liver, which synthesizes this substance.Also, urea can increase or decrease with a number of infectious diseases, with some autoimmune pathologies, after injuries or against the background of hormonal disruptions. In each case, the patient will have corresponding disorders. Deviations in the analysis of urea are not directly related to these diseases and only indirectly confirm the diagnosis.
Thus, the attending physician should deal with the interpretation of the results of the analysis for urea. Only a qualified specialist will be able to notice all the symptoms and interpret them correctly to make the correct diagnosis.
Why determine urea in daily urine?
Unlike a blood test for urea, where the concentration of this substance is determined, in the analysis of urine, the total amount of urea excreted is put in first place. The concentration here is not critical, as there are too many factors that affect the functioning of the kidneys. For example, with excessive fluid intake, the concentration of urea will be very low, and with dehydration, the concentration will be high. It is noticed that only the total amount of urea that is excreted from the body per day remains at the same level. That is why the indicator “the amount of urea in daily urine” appears in the results of the analysis, and not its concentration.Symptoms of high and low urea
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With a high level of urea, the patient has the following complaints:
- moderate headaches;
- general weakness;
- sleep problems, etc.
In some cases, the concentration of urea in the blood rises simultaneously with the concentration of other substances. As a rule, this occurs with a severe violation of the kidneys. In these cases, the symptoms and manifestations of the disease can be very severe, but their appearance is caused not so much by an excess of urea in the blood, but by general intoxication and concomitant disorders. In severe cases, patients may experience vomiting, convulsions, diarrhea, a tendency to bleed, etc. Without qualified medical care, the patient may fall into a uremic coma.
Does urea have a harmful effect on the body?
By itself, urea is not a toxic substance and does not have a direct negative effect on the body. That is why it is "used" by the body as a safe form of excretion of more toxic substances ( other nitrogenous compounds). Most of the symptoms that appear in patients with high urea levels are associated with parallel intoxication with other substances against the background of renal failure.Of the harmful effects of urea itself, one can note the accumulation of fluid in the tissues ( swelling is possible). This is due to the fact that urea is an osmotically active substance. Its molecules are able to "attract" water molecules to themselves. At the same time, urea molecules are small and can pass through cell membranes. Thus, at a high concentration of urea, fluid retention in the tissues is possible.
Why is urea and its salts dangerous for gout?
Contrary to popular belief, gout does not retain urea in the body, but uric acid, another nitrogen compound. In a healthy body, uric acid does not play a serious physiological role and is of secondary importance. With gout, the salts of this substance begin to accumulate in the tissues with the formation of characteristic foci ( tophi). Urea is not directly related to the development of this disease.Is it dangerous to increase urea in diabetes?
Diabetes mellitus is a serious disease that affects many processes in the body. Patients with this pathology are recommended to take regular blood and urine tests in order to notice the deterioration and various complications in time. As part of a biochemical blood test, urea can indicate very serious problems. For example, in advanced diabetes, some patients develop ketoacidosis ( ketone bodies appear in the blood, and the pH of the blood changes). As a result, the urea level may begin to rise. Also, diabetes can damage the kidneys ( diabetic nephropathy). The result may be a deterioration in blood filtration and urea retention in the body.Thus, an elevated urea level in diabetic patients usually indicates a deterioration in their condition. If you receive such a result, it is recommended to immediately contact your doctor ( endocrinologist) to stabilize the situation.
Treatment for low and high urea
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Most often with increased or decreased urea ( depending on test results) begin treatment in the following areas:
- hemodialysis and the introduction of drugs to cleanse the blood of toxic decay products ( usually in renal failure);
- treatment of causes of kidney failure;
- restoration of liver function hepatitis treatment, etc.);
- normalization of hormonal background ( with disorders of the thyroid or pancreas) and etc.
What pills and medicines are used to lower the level of urea?
Reducing the level of urea in the blood is not the main goal of the course of treatment. First of all, doctors try to normalize the functioning of the kidneys, liver or other organs that have led to the accumulation of nitrogenous compounds in the blood. With proper and effective treatment, the level of urea in the blood gradually decreases on its own. In rare cases, when a patient has severe azotemia ( very high concentrations of urea and other toxic nitrogen compounds in the blood), prescribed drugs for blood purification.The following drugs are most effective for severe azotemia:
- lespenephril;
- hepa-merz;
- ornilatex;
- ornitsetil;
- larnamine.
Also, with severe intoxication with urea and other nitrogen compounds, the patient can be given drip special solutions that help cleanse the blood, or do hemodialysis ( blood purification using a special filtration apparatus).
Is it possible to treat increased urea with folk remedies?
By itself, increased urea is not a pathology. This is just one of the manifestations of any disease or abnormality in the work of internal organs. That is why treatment should be aimed not so much at lowering the level of urea as at eliminating the cause of this deviation. Urea itself, in principle, can decrease under the influence of some folk remedies. This is due to the stimulation of its natural excretion from the body ( with urine) and partially by binding. It should be noted that folk remedies do not always help. If, for example, urea is elevated due to kidney failure, then stimulation with diuretic decoctions will only worsen the situation. That is why patients with elevated urea levels are advised to consult a doctor before using any means ( including folk).In general, there are the following folk methods that will help reduce urea in the blood:
- Decoction of licorice root. For 2 tablespoons you need 1 liter of water. Licorice root is poured and boiled for 2-3 minutes. After that, the broth is cooled and drunk half a cup twice a day before meals.
- Bearberry infusion. 2 tablespoons of bearberry herb pour boiling water ( 0.5 l) and insist 4 - 5 hours. The decoction is taken 1 tablespoon 3 times a day before meals.
- Rosehip tea. Rosehip tea can be prepared on your own by picking berries, or purchased at a pharmacy in the form of a special collection. This remedy stimulates the formation of urine, but may be contraindicated in some kidney diseases.
- A decoction of hernia and field horsetail. A mixture of dry herbs hernia and field horsetail ( 3 - 5 g) pour 0.5 liters of water and boil for 5 - 7 minutes over low heat. The cooled broth is drunk before meals for half a glass.
- Infusion of black currant leaves. Young blackcurrant leaves are harvested and dried in the sun for several days. After that, they make an infusion in a large container ( about 8 large sheets per 1 liter of water). Infusion should last 3 - 5 days. The resulting infusion is drunk 1 cup twice a day for 2 to 3 weeks.
How to lower the level of urea at home?
Reducing the level of urea at home is usually not required, since this substance does not pose a serious threat to the body. If an increased concentration of this substance is found in the analyzes, you should consult a doctor to diagnose the underlying pathology ( reasons for the increase). Depending on the disease, the doctor will be able to develop treatment tactics and give recommendations on home prevention. By itself, a decrease in urea will not solve the problem, but only eliminate one of the manifestations of the disease.What to do if urea is low?
Decreased levels of urea in the blood and urine are rare. This does not always indicate serious pathologies. To correctly interpret the results of the analysis, you need to contact a specialist. In some cases, low urea does not require any treatment. For example, a vegetarian diet contains less protein. In people who adhere to it, less urea is formed in the body. Accordingly, its level may be slightly lower than normal in both blood and urine.If the concentration of urea is lowered for a long time for no apparent reason, the following tactics are possible:
- consultation with a general practitioner or family doctor;
- urologist's consultation if the level in the urine is low) or hepatologist ( if blood urea is low);
- additional laboratory and instrumental tests to assess the functioning of the liver and kidneys.
Preparations with urea
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In addition, urea has a keratolytic effect ( affects the stratum corneum). This action is widely used in dermatology and cosmetology to soften the skin. There are quite a few skin care products that contain urea.
What are urea creams and ointments used for?
Creams and ointments containing urea are mainly used to soften rough skin. Such funds act on the stratum corneum of the skin, destroying dead cells. As a result, the skin becomes softer. Ointments with a high concentration of urea ( e.g. uroderm) can also be used to soften dry calluses. In some cases, they are prescribed for edema of the limbs ( urea compounds “pull” fluid out of tissues) and a number of dermatological pathologies ( psoriasis, eczema, ichthyosis, etc.).As a rule, pharmaceutical and cosmetic products with urea for external use can be used without a special prescription from a doctor. They are practically not absorbed into the bloodstream and do not have a serious effect on the concentration of urea in the blood and urine.
How to use preparations with urea for legs and heels?
Creams and ointments with urea are widely used to care for the skin of the feet and nails. With coarsening of the skin on the heels, dry calluses or cracks, the ointment is applied to the problem area 2-3 times a day with a thin layer. It is better to wash the skin with warm water before applying the product. With corns, urea-based ointments can be applied under anti-corn patches.For fungal diseases of the nails and skin on the legs, urea preparations are used in parallel with prescribed antifungal agents.
Ammonia, in one way or another, entered the liver or formed in hepatocytes enters the urea cycle, discovered in 1932.
The synthesis of urea begins with the formation of carbomoyl phosphate in the mitochondria of the liver.
The second reaction of urea formation also proceeds in mitochondria (transferase ensures the transfer of the carbomonyl residue to the arnitine-monocarboxylic acid molecule containing 5 carbon atoms). The amino acid citrulline is formed.
Further urea formation reactions take place in the cytosol. The following reaction involves citrulline and aspartate (the enzyme argininosuccinate synthetase). This reaction involves citrulline and aspartate. The reaction is energy dependent. During the reaction, ATP is cleaved to AMP and pyrophosphate and argininosuccinic acid or argininosuccinate is formed.
Where do cells find aspartate from? Aspartate is formed during transamination reactions from oxaloacetate, an intermediate product of the Krebs cycle, which undergoes a reaction with glutamate to form aspartate.
Further, during the next process, a lyase reaction occurs (lyase cleavage - cleavage in a non-hydrolytic way) (enzyme - argininosuccinate lyase). Cleavage occurs and, as a result, the amino acid arginine is formed and the residue is cleaved off in the form of fumaric acid.
Fumaric acid is an intermediate product of the Krebs cycle, by adding water it turns into malate, malate is dehydrated and turns into oxaloacetate, and oxaloacetate can turn into aspartate due to transamination, which supplies one nitrogen atom.
The last reaction of urea formation is catalyzed by an enzyme with absolute specificity, arginise. There is a splitting of arginine, a complete carbonic acid amide called urea is formed and regenerates ornithine. Hence the name of the cycle - the ornithine cycle of urea formation.
In the course of the next reaction, arnitine, again reacting with carbomoyl phosphate, can give citrulline, and further repetition of the reactions leads to an increase in the synthesized urea.
The irreversible reaction in this process is the reaction involving argininosuccinate synthetase - thermodynamic control of the direction of the process as a whole.
Synthesis comes from carbon dioxide, ammonia,
The source of carbon in urea is undoubtedly carbon dioxide. One nitrogen atom comes from ammonia, and the second nitrogen atom comes from aspartate. For the synthesis of 1 molecule of urea, the cell spends 4 macroergic equivalents. Normally, the concentration of urea in the blood is 3.3-8.3 mlmol / l. Moreover, urea nitrogen makes up approximately 50% of all non-protein nitrogen in the blood.
The daily excretion of urea from the body is 20-35 gr. The enzyme arginase, like arginine, is also present in other tissues such as the brain, kidneys, and skin. However, in quantitative terms, the formation of urea in these organs is extremely small.
It should be noted that the amount of urea excreted in the urine depends on several factors.
n The amount of excreted urea will also decrease in case of kidney pathology, which is accompanied by a retention of nitrogenous slags in the body.
n Urea excretion may decrease in severe liver disease as a result of impaired urea synthesis.
Excretion of ammonia in the form of ammonium salts by the kidneys.
Glutamine - the main product in the form of which ammonia is transported in the kidneys, undergoes hydrolysis with the participation of the enzyme - glutaminase.
As a result, ammonia is formed, which, being a base, easily forms the ammonium ion. Further, the ammonium ion interacts with anions, resulting in the formation of ammonium salts.
Thus, the excretion of each ammonia molecule in the urine is accompanied by the capture of a proton, i.e. excretion of ammonia is accompanied simultaneously with the excretion of acid equivalents from the body.
It turns out that renal glutominis is an inducible enzyme. Enzyme synthesis is activated with the accumulation of acid equivalents in the blood or otherwise with the development of acidosis. As a result, there is an increase in the excretion of ammonium salts in the urine, and with them acid equivalents. Those. we are dealing with a typical defensive reaction of the body aimed at compensating for acidosis that has arisen for one reason or another. Therefore, with acidosis, the amount of ammonium salts excreted in the urine increases dramatically. While with alkalosis, a person practically completely stops their formation.
Urea is the main end product of nitrogen metabolism, which removes excess nitrogen from the body. Excretion of urea is normally about 25 g / day. It is synthesized only in the liver. Amino acid catabolism and ammonia formation occur in many tissues. Three compounds are used to transport nitrogen from tissues to the liver: glutamine, alanine, and ammonia.
Ornithine cycle(Krebs-Henseleit cycle) in the liver performs 2 functions:
The conversion of amino acid nitrogen into urea (which is excreted and prevents the accumulation of toxic products - ammonia)
Synthesis of arginine and replenishment of its fund in the body
A complete set of enzymes of the ornithine cycle is found only in hepatocytes.
In the formation of 1 mol of urea, 1 mol of NH4+, 1 mol of CO2 (activated by Mg2+ and ATP) and 1 mol of α-amine nitrogen of aspartate participate. During the synthesis, 3 moles of ATP are consumed (2 of them are converted into ADP and Pi, and the third into AMP and PPi), 5 enzymes sequentially participate in it. The amino acids aspartate, arginine, ornithine, circulline, and argininosuccinate serve as carriers of atoms that eventually form the urea molecule. The amino acid N-acetylglutamate is also involved in the synthesis of urea; it serves as an activator of one of the enzymes and does not participate in chemical transformations.
The formation of urea is partly a cyclic process. Ornithine (involved in the 2nd reaction) is regenerated during the 5th reaction. That. neither loss nor accumulation of ornithine, citrulline, arginiosuccinate and arginine occurs during synthesis - only ammonium ion, CO2, ATP and aspartate are consumed.
Reaction 1:synthesis of carbomoyl phosphate. Condensation of ammonium, CO2 and phosphate (comes from ATP) leading to the formation of carbamoyl phosphate. The enzyme carbamoyl phosphate synthase is found in the mitochondria of the liver. During the reaction, hydrolysis of 2ATP occurs, providing energy for the formation of 2 covalent bonds (amide and anhydride in the formation of carbamoyl phosphate from carboxylic and phosphoric acids). This reaction requires Mg2+ ions and a dicarboxylic acid (preferably N-acetylglutamate). In the presence of these compounds, conformational changes in carbamoyl phosphate synthase occur and the affinity of the enzyme for ATP increases.
Reaction 2:citrulline synthesis. Transfer of the carbamoyl group from carbamoyl phosphate to ornithine to form citrulline and Pi. The enzyme ornithine carbamoyl transferase is located
in the mitochondria of the liver.
Reaction 3:synthesis of argininosuccinate. The amino group aspartate is attached to citrulline. Enzyme arginino-succinate-synthase. The reaction requires ATP. The reaction takes place in the cytosol.
Reaction 4: splitting of argininosuccinate into arginine and fumarate. The enzyme argininosuccinate lyase. The reaction of trans-elimination. The resulting fumarate can turn into oxaloacetate (malate dehydrogenase), oxaloacetate turns into aspartate upon transamination.
In order for the human body to maintain normal life, it has developed mechanisms for the elimination of toxic substances. Among them, ammonia is the end product of the metabolism of nitrogenous compounds, primarily proteins. NH 3 is toxic to the body, and, like any poison, is excreted through the excretory system. But before ammonia undergoes a series of successive reactions, which is called the ornithine cycle.
Types of nitrogen metabolism
Not all animals are characterized by the release of ammonia into the environment. Urea is also an alternative end product of nitrogen metabolism. Accordingly, three types of nitrogen metabolism are called, depending on the substance released.
Ammoniotelic type. The final substance here is a colorless gas soluble in water. Ammoniothelia is characteristic of all fish that live in salt water.
Ureotelic type. Animals that are characterized by ureothelia release urea into the environment. Examples are freshwater fish, amphibians and mammals, including humans.
uricotelic type. This includes those representatives of the animal world in which the final metabolite is This substance as a product of nitrogen metabolism is found in birds and reptiles.
In any of these cases, the task of the end product of metabolism is the removal of unnecessary nitrogen from the body. If this does not occur, cell taxation and inhibition of important reactions are observed.
Urea is an amide of carbonic acid. It is formed from ammonia, carbon dioxide, nitrogen and amino groups of certain substances during the reactions of the ornithine cycle. Urea is a product of the excretion of ureotelic animals, including humans.
Urea is one way to excrete excess nitrogen from the body. The formation of this substance has a protective function, because. the precursor of urea, ammonia, is toxic to human cells.
When processing 100 g of protein of various nature, 20-25 g of urea is excreted in the urine. The substance is synthesized in the liver, and then with the blood flow enters the nephron of the kidney and is excreted along with the urine.
The liver is the main organ for the synthesis of urea.
In the entire human body, there is no such cell in which absolutely all the enzymes of the ornithine cycle will be present. Except for hepatocytes, of course. The function of liver cells is not only in the synthesis and destruction of hemoglobin, but also in carrying out all reactions of urea synthesis.
Under the description of the ornithine cycle fits the fact that it is the only way to remove nitrogen from the body. If, in practice, the synthesis or action of the main enzymes is inhibited, the synthesis of urea will stop, and the body will die from an excess of ammonia in the blood.
ornithine cycle. Biochemistry of reactions
The urea synthesis cycle takes place in several stages. The general scheme of the ornithine cycle is presented below (picture), so we will analyze each reaction separately. The first two stages take place directly in the mitochondria of liver cells.
NH 3 reacts with carbon dioxide using two ATP molecules. As a result of this energy-consuming reaction, carbamoyl phosphate is formed, which contains a macroergic bond. This process is catalyzed by the enzyme carbamoyl phosphate synthetase.
Carbamoyl phosphate reacts with ornithine by the enzyme ornithine carbamoyl transferase. As a result, it is destroyed, and due to its energy, citrulline is formed.
The third and subsequent stages take place not in mitochondria, but in the cytoplasm of hepatocytes.
There is a reaction between citrulline and aspartate. With the expenditure of 1 ATP molecule and under the action of the enzyme arginine-succinate synthase, arginine-succinate is formed.
Arginino-succinate, together with the enzyme arginino-succin-lyase, is broken down to arginine and fumarate.
Arginine in the presence of water and under the action of arginase is cleaved to ornithine (1 reaction) and urea (final product). The cycle is closed.
Energy cycle of urea synthesis
The ornithine cycle is an energy-consuming process in which macroergic bonds of adenosine triphosphate (ATP) molecules are consumed. During all 5 reactions, 3 ADP molecules are formed in total. In addition, energy is spent on the transport of substances from the mitochondria to the cytoplasm and vice versa. Where does ATP come from?
The fumarate formed in the fourth reaction can be used as a substrate in the tricarboxylic acid cycle. During the synthesis of malate from fumarate, NADPH is released, which results in 3 ATP molecules.
The glutamate deamination reaction also plays a role in supplying liver cells with energy. At the same time, 3 ATP molecules are also released, which go to the synthesis of urea.
Regulation of ornithine cycle activity
Normally, the cascade of urea synthesis reactions functions at 60% of its possible value. With an increased protein content in food, reactions are accelerated, which leads to an increase in overall efficiency. Metabolic disorders of the ornithine cycle are observed during high physical exertion and prolonged fasting, when the body begins to break down its own proteins.
The regulation of the ornithine cycle can also occur at the biochemical level. Here the target is the main enzyme carbamoyl phosphate synthetase. Its allosteric activator is N-acetyl-glutamate. With its high content in the body, urea synthesis reactions proceed normally. With a lack of the substance itself or its precursors, glutamate and acetyl-CoA, the ornithine cycle loses its functional load.
Relationship between the urea synthesis cycle and the Krebs cycle
The reactions of both processes take place in the mitochondrial matrix. This makes it possible for some organic substances to participate in two biochemical processes.
CO 2 and adenosine triphosphate, which are formed in the citric acid cycle, are precursors of carbamoyl phosphate. ATP is also the most important source of energy.
The ornithine cycle, whose reactions take place in the hepatocytes of the liver, is a source of fumarate, one of the most important substrates. Moreover, this substance, as a result of several stepwise reactions, gives rise to aspartate, which, in turn, is used in the biosynthesis of the ornithine cycle. The reaction involving fumarate is the source of NADP, which can be used to phosphorylate ADP to ATP.
The biological meaning of the ornithine cycle
The vast majority of nitrogen enters the body in the composition of proteins. The amino acids are destroyed, ammonia is formed as the end product of metabolic processes. The ornithine cycle consists of several successive reactions, the main task of which is to detoxify NH 3 by converting it into urea. Urea, in turn, enters the nephron of the kidney and is excreted from the body in the urine.
In addition, by-product of the ornithine cycle is a source of arginine, one of the essential amino acids.
Violations in the synthesis of urea can lead to a disease such as hyperammonemia. This pathology is characterized by an increased concentration of ammonium ions NH 4 + in human blood. These ions adversely affect the life of the body, turning off or slowing down some important processes. Ignoring this disease can lead to death.
(ORNITHINE CYCLE).
Only in fish, ammonia is the final breakdown product and is excreted from the body. In birds and reptiles, the catabolism end product of nitrogen compounds is uric acid, not ammonia. In mammals, the resulting ammonia is converted to urea - this is a complete amide of carbonic acid:
The synthesis of urea is a cyclic process, in which pre-synthesized carbamoyl phosphate and aspartate enter, and fumarate and urea are formed.
Urea is synthesized from one molecule of CO 2 , one molecule of NH 3 and the amino group of aspartate. From fumarate in the reactions of TCA, oxaloacetic acid is again formed, which can enter into transamination with other amino acids and turn into aspartate.
Thus, there are two conjugated cycles in the ornithine cycle:
a) the formation of urea; b) regeneration of aspartate.
In addition to the lecture on general pathways of amino acid metabolism, one more, third function of transamination is the transfer of an amino group from amino acids for the synthesis of urea without the intermediate release of ammonia.
In the synthesis of urea, a total of 4 ATP molecules are consumed. Urea is a non-toxic substance that is easily excreted from the body in the urine. The accumulation of urea in the blood above the norm occurs only with impaired renal function.
The synthesis of urea occurs only in the liver, and ammonia is formed in various tissues. This means that there must be a special mechanism for the transport of ammonia in a form that is harmless to the body: this is a MECHANISM FOR THE TEMPORARY NEUTRALIZATION OF AMMONIA.
It is provided by the enzyme glutamine synthetase, which attaches an additional amino group to the gamma carboxy group at the expense of ATP:
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The amino group can also attach to aspartate - to the beta carboxy group.
Particularly important are the reactions of temporary neutralization of ammonia in the nervous tissue (very sensitive to the toxic effects of ammonia). They also proceed with considerable speed in muscle tissue.
The resulting amides are transferred to the liver, where they donate amide nitrogen for urea synthesis. In the kidneys, a certain amount of ammonia from amides can be released in a free form. Usually, a little of this ammonia is formed, but if there is acidosis in the body - a shift in pH to the acid side, then this ammonia begins to be excreted in the urine in large quantities. Ammonia allows you to partially neutralize the acids that pass from the blood into the urine during acidosis. Thus, glutamine and asparagine are transport forms of ammonia and, as part of their molecule, transfer it from different tissues to the liver and kidneys.