Acid-base homeostasis. Acid-base balance. Can the body always support it? Acidosis or alkalosis, which is better? Symptoms and regulation. A review of research, views and opinions, scientists and ordinary people. Basic principles of WWTP regulation
Acid-base state- one of the most important physical and chemical parameters of the internal environment of the body. In the body of a healthy person, acids are constantly formed daily during the metabolic process - about 20,000 mmol of carbonic acid (H 2 C0 3) and 80 mmol of strong acids, but the concentration of H + fluctuates in a relatively narrow range. Normally, the pH of the extracellular fluid is 7.35-7.45 (45-35 nmol/l), and the extracellular fluid averages 6.9. At the same time, it should be noted that H + inside the cell is heterogeneous: it is different in the organelles of the same cell.
H+ are so capable that even a short-term change in their concentration in the cell can significantly affect the activity of enzyme systems and physiological
processes. However, normally, buffer systems are instantly activated, protecting the cell from unfavorable pH fluctuations. The buffer system can bind or, conversely, release H + immediately
in response to changes in the acidity of the intracellular fluid.
Buffer systems also operate at the level of the organism as a whole, but, in
Ultimately, the regulation of the body's pH is determined by the functioning of the lungs and kidneys.
So what is it acid-base state (synonyms: acid-base balance, acid-base state, acid-base balance, acid-base homeostasis). This is the relative constancy of the pH value of the internal environment of the body, due to the combined action of the buffer and some physiological systems of the body (Encyclopedic Dictionary of Medical Terms, vol. 2, p. 32).
Acid-base balance is the relative constancy of the hydrogen index (pH) of the internal environment of the body, due to the combined action of buffer and some physiological systems, which determines the usefulness of metabolic transformations in the cells of the body (BME, vol. 10, p. 336).
The ratio of hydrogen and hydroxyl ions in the internal environment of the body depends on:
1) enzyme activity and intensity of redox reactions;
2) processes of hydrolysis and protein synthesis, glycolysis and oxidation of carbohydrates and fats;
3) sensitivity of receptors to mediators;
4) membrane permeability;
5) the ability of hemoglobin to bind oxygen and release it to tissues;
6) physicochemical characteristics of colloids and intercellular structures: the degree of their dispersity, hydrophilia, adsorption ability;
7) functions of various organs and systems.
The ratio of H + and OH" in biological media depends on the content of acids (proton donors) and buffer bases (proton acceptors) in body fluids. The active reaction of the medium is assessed by one of the ions (H + or OH-), most often by H +. The H+ content in the body depends on their formation during the metabolism of proteins, fats and carbohydrates, as well as their entry into the body or removal from it in the form of non-volatile acids or carbon dioxide.
The pH value, which characterizes the state of the CBS, is one of the most “hard” blood parameters and varies in humans within very narrow limits: from 7.3 5 to 7.45l. A pH shift of 0.1 beyond the specified limits causes pronounced disturbances in the respiratory, cardiovascular system, etc., a decrease in pH by 0.3 results in acidotic coma, and a pH shift of 0.4 is often incompatible with life.
The exchange of acids and bases in the body is closely related to the exchange of water and electrolytes. All these types of exchange are united by the law of electrical neutrality, isosmolarity and homeostatic physiological mechanisms.
The total amount of plasma cations is 155 mmol/l (Na+ - 142 mmol/l; K+ - 5 mmol/l; Ca 2+ - 2.5 mmol/l; Mg 2 + 0.5 mmol/l; other elements - 1 .5 mmol/l), and the same amount of anions is contained (103 mmol/l - weak base CI ~; 27 mmol/l - strong base HCO, -; 7.5-9 mmol/l - protein anions; 1.5 mmol /l - phosphate anions; 0.5 mmol/l - sulfate anions; 5 mmol/l - organic acids). Since the H+ content in plasma does not exceed 40x10 -6 mmol/l, and the main plasma buffer bases (HCO3-) protein anions are about 42 mmol/l, the blood is considered a well-buffered medium and has a slightly alkaline reaction.
Rental block
All buffer systems of the body are involved in maintaining acid-base homeostasis (the balance of optimal concentrations of acidic and basic components of physiological systems). Their actions are interconnected and are in a state of balance. The hydrocarbonate buffer is most associated with all buffer systems. Disturbances in any buffer system affect the concentrations of its components, so changes in the parameters of the hydrocarbonate buffer system can quite accurately characterize the body's CBS.
Blood CBS is normally characterized by the following metabolic parameters:
Plasma pH 7.4±0.05;
[HCO3-]=(24.4±3) mol/l - alkaline reserve;
рСО2=40 mm Hg - partial pressure of CO2 above the blood.
From the Henderson-Hasselbach equation for a bicarbonate buffer, it is obvious that when the concentration or partial pressure of CO2 changes, the blood CBS changes.
Maintaining the optimal value of the environmental reaction in various parts of the body is achieved through the coordinated work of buffer systems and excretory organs. A shift in the reaction of the medium to the acidic side is called acidosis, and basically – alkalosis. The critical values for preserving life are: a shift to the acidic side to 6.8, and to the basic side – 8.0. Acidosis and alkalosis can be respiratory or metabolic in origin.
Metabolic acidosis develops due to:
a) increased production of metabolic acids;
b) as a result of loss of bicarbonates.
Increased production of metabolic acids occurs with: 1) type I diabetes mellitus, prolonged, complete fasting or a sharp reduction in the proportion of carbohydrates in the diet;
2) lactic acidosis (shock, hypoxia, type II diabetes mellitus, heart failure, infections, alcohol poisoning).
Increased loss of bicarbonates is possible in the urine (renal acidosis), or with some digestive juices (pancreatic, intestinal).
Respiratory acidosis develops with hypoventilation elation of the lungs, which, regardless of the cause that caused it, leads to an increase in the partial pressure of CO2 to more than 40 mm Hg. Art. (hypercapnia). This happens with diseases of the respiratory system, hypoventilation of the lungs, depression of the respiratory center with certain drugs, for example, barbiturates.
Metabolic alkalosis observed with significant losses gastric juice due to repeated vomiting, as well as as a result of the loss of protons in the urine during hypokalemia, constipation (when alkaline products accumulate in the intestines; the source of bicarbonate anions is the pancreas, the ducts of which open into the duodenum), as well as during prolonged taking alkaline foods and mineral water, the salts of which undergo hydrolysis by anion.
Respiratory (respiratory) alkalosis develops as a result of hypervelocity Ntilation of the lungs, leading to excessive removal of CO2 from the body and a decrease in its partial pressure in the blood to less than 40 mm. Hg Art. (hypocapnia). This happens when inhaling rarefied air, hyperventilation of the lungs, the development of thermal shortness of breath, excessive excitation of the respiratory center due to brain damage.
For acidosis as an emergency measure use intravenous infusion of 4–8% sodium bicarbonate, 3.66% solution of trisamine H2NC(CH2OH)3 or 11% sodium lactate. The latter, while neutralizing acids, does not emit CO2, which increases its effectiveness.
Alkaloses are more difficult to correct, especially metabolic ones (associated with disruption of the digestive and excretory systems). Sometimes a 5% solution of ascorbic acid is used, neutralized with sodium bicarbonate to pH 6 - 7.
Alkaline reserve- this is the amount of bicarbonate (NaHC03) (more precisely, the volume of CO2 that can be bound by blood plasma). This value can only conditionally be considered as an indicator of acid-base balance, since, despite the increased or decreased bicarbonate content, in the presence of appropriate changes in H2CO3, the pH can remain completely normal.
Since compensatory possibilities through breathing, initially used by the body, are limited, the decisive role in maintaining constancy passes to the kidneys. One of the main tasks of the kidneys is to remove H+ ions from the body in cases where, due to some reason, a shift towards acidosis occurs in the plasma. Acidosis cannot be corrected unless the appropriate amount of H ions is removed. The kidneys use 3 mechanisms:
1. Exchange of hydrogen ions into sodium ions, which, combining with the HCO3 anions formed in the tubular cells, are completely reabsorbed in the form of NaHCO,
The prerequisite for the release of H-ions using this mechanism is the carbonic anhydrase-activated reaction CO2 + H20 = H2CO3, and H2CO3 decomposes into H and HCO3 ions. In this exchange hydrogen ions to ions sodium, reabsorption of all sodium bicarbonate filtered in the glomeruli occurs.
2. Excretion of hydrogen ions in urine and the reabsorption of sodium ions also occurs by converting the alkaline salt of sodium phosphate (Na2HP04) into the acid salt of sodium diphosphate (NaHaPO4) in the distal tubules.
3. Formation of ammonium salts: ammonia, formed in the distal parts of the renal tubules from glutamine and other amino acids, promotes the release of H-ions and the reabsorption of sodium ions; NH4Cl is formed due to the combination of ammonia with HCl. The intensity of ammonia formation, necessary to neutralize strong HCl, is greater, the higher the acidity of the urine.
Table 3
Basic parameters of CBS
(average value in arterial blood)
40 mm. Hg Art.
(partial pressure of CO2 in blood plasma)
This component directly reflects the respiratory component in the regulation of CBS (CAR).
(hypercapnia) is observed with hypoventilation, which is characteristic of respiratory acidosis.
↓ (hypocapnia) is observed during hyperventilation, which is characteristic of respiratory alkalosis. However, changes in pCO2 may also be a consequence of compensation from metabolic disorders of the CBS. To distinguish these situations from each other, it is necessary to consider pH and [HCO3-]
95 mm. Hg Art. (partial pressure in blood plasma)
SB or SB
SB – standard plasma bicarbonate i.e. [НСО3-] ↓ - with metabolic acidosis, or with compensation of respiratory alkalosis.
For metabolic alkalosis or compensation for respiratory acidosis.
Additional indexes
BO or BB
(base buffers)
Buffer bases. This is the sum of all whole blood anions belonging to buffer systems.
BEFORE or BD
(base deficiency)
Base deficiency. This is the difference between the practical and proper BO value in metabolic acidosis. Defined as the number of bases that must be added to the blood to bring its pH to normal (at pCO2 = 40 mmHg tо = 38°C)
IO or BE
(base excess)
Base excess. This is the difference between the actual and expected BO values in metabolic alkalosis.
Normally, relatively speaking, there is neither a deficiency nor an excess of bases (neither DO nor IO). In fact, this is expressed in the fact that the difference between the expected and actual BO is under normal conditions within ±2.3 meq/l. The departure of this indicator from the normal range is typical for metabolic disorders of CBS. Abnormally high values are typical for metabolic alkalosis. Abnormally low – for metabolic acidosis.
Laboratory and practical work
Experience 1. Comparison of the buffer capacity of blood serum and phosphate BS
Measure ml
N flask
Blood serum (1:10 dilution)
Phosphate BS (diluted 1:10), pH = 7.4
Phenolphthalein (indicator)
Hello dear friends!
Today I would like to once again draw your attention to the main causes of our diseases. Most people continue to live absolutely incorrectly, without weighing the facts and without reflecting on the essence of their existence. They live like tumbleweeds, rolling with the wind of life, exchanging the days and years of their existence for vanity of vanities. They do not think about tomorrow, they do not try not only to somehow plan and predict their future, but even to dream about it. And of course, against the backdrop of such an existence, there is no room left for your health. Such people simply don’t think about it, knowing that there are doctors and clinics who will help.
What can you say about this? Rely on God, but you yourself are a bad guy! Hope in this case is absolutely the wrong approach to your own life. Our medicine in such cases is just an ambulance. And the result of such assistance, at best, can be fifty-fifty. There are no guarantees that you will not die after the first bell. The driver's ideology - where the road will take you - is not at all for those who intend to live long, interestingly and happily.
If you care when you pass into another world, or how many years before your death you will suffer with your sores, start taking care of yourself right today. And I am very glad if you have already understood how to treat yourself and your health and do everything systematically throughout the slowly flowing time of your life. Of course, we are talking primarily about your own actions aimed at creating your happy future and maintaining health for many, many years.
The key to health is your metabolism - homeostasis. And let's talk today about its parts that can be adjusted. A person must learn to manage his own health. And today there are all conditions for this! Well, let's hit the road? Most importantly, without lyrics and digressions. It is clear that this topic is worthy of a separate publication, but in this short article I will try to teach you to move in the right direction in order to maintain health and recovery. So, let's go...
The basic, basic chemical processes of the body are manifested in the interaction of acid and alkali,
which occur in the human body in a changing rhythm. A person with a normal blood pH level of 7.35 is an alkaline living being.
What is “pH level” anyway?
This important measuring number forms the basis of the acid-base balance, which has
crucial not only for nature, but also for the basic regulation of human life. Acid-base balance, regulates breathing, blood circulation, digestion, excretory processes, immunity,
hormone production and much more. Almost all biological processes proceed correctly only when
when a certain pH level is maintained.
The acid-base balance is constantly maintained in the body, in all cells of the body. In each of these cells, during their life, during the production of energy, carbon dioxide is constantly formed. At the same time, other acids appear that enter the body and are formed in it when food is consumed, bad habits, stress and anxiety.
There is a pH scale that can be used to determine how acidic or alkaline something is.
is any solution, including any physiological fluid - blood, saliva or urine.
We all know the chemical formula of water – H2O. Those who have not completely forgotten chemistry remember that if we look at the structure of this formula, we will see the following picture: H-OH, where H is a positively charged ion, and the OH group is a negatively charged ion.
Thus, we see in the composition of water there is not only an “acidic” hydrogen ion, but also an “alkaline” connection of a hydrogen atom with an oxygen atom, which create a stable bond called a “hydroxyl group”.
Thus, the formula of water is represented by two ions, which are present here in equal amounts
quantity - one negative and one positive, as a result of which we have chemically
neutral substance. Point 7 of the pH scale is precisely this indicator of neutrality. That is, this is the pH indicator of distilled (pure) water.
In general, the pH scale is divided from 0 to 14.
At pH 0, we are dealing with the highest concentration of positively charged hydrogen ions and almost zero concentration of negative OH ions, while at pH14, hydrogen ions are almost never found, and the index of OH ions reaches its maximum.
Thus, below pH 7, simple hydrogen cations (+ H) predominate. Above pH 7, hydroxyl group anions (-OH) predominate.
The lower the pH value from mark 7 to 0, the more acidic the liquid is, and vice versa, the higher the pH value from mark 7 to mark 14, the greater the manifestation of alkalinity. The number of hydrogen ions always determines the concentration or the so-called degree of acid, i.e. The more simple hydrogen ions, the more acidic the liquid. This is why the abbreviation pH comes from the Latin Potentia Hydrogenii, meaning “the power of hydrogen.” To put it in a language that is more understandable to ordinary people, this is simply an indicator of the power (concentration) of the acid. The strength of acidity decreases from 1 to 7, and then comes the domain of alkali.
A logarithmic sequence of values is hidden in the pH level measuring scale from 0 to 14.
This means, for example, that a pH value of 6 indicates an acid strength ten times greater than a pH value of 7, and a pH of 5 is already a hundred times greater than a pH of 7, and a pH of 4 is already a thousand times greater than a pH of 7.
The basis of our life - our blood - has a pH value from 7.35 to 7.45, that is, it is slightly alkaline.
Acids and alkalis are in a very close relationship in the body.
They must be in balance, with a slight preponderance on the alkaline side, since we humans belong to the “alkaline caste of the kingdom of nature.”
The vitality and health of a person depends on regularly drinking a sufficient amount of high-quality water and alkaline compounds - minerals and trace elements, otherwise the normal pH level of the blood would not be in the indicated vital range of 7.35 - 7.45.
This zone can be disturbed only slightly, otherwise a critical, life-threatening condition may occur. To prevent strong fluctuations in this pH value, the human metabolism has various buffer systems. One of them is the hemoglobin buffer system. It immediately decreases if, for example, anemia occurs or microcirculation is disrupted at the cellular level, when clumped clusters of red blood cells are unable to penetrate the capillaries and bring the cells a sufficient amount of oxygen to normalize energy metabolic processes in them and remove carbon dioxide from them ( CO2).
The reason for the formation of sludge (sticking together) of red blood cells is essentially two reasons - a chronic lack of water in the body (constant lack of drinking, thirst) and acidic foods, including all kinds of drinks that carry an excess of positively charged ions, removing the vital negative potential from the outside of the shell red blood cells (charge neutralization). Since metabolic processes between the internal and external environments in cells occur due to the difference in electrical potentials (minus outside, plus inside), the aggression of positively charged ions sharply reduces the vitality of cells (in particular red blood cells, all leukocytes and other cells). Cells moving freely in the blood, having lost vital energy, begin to precipitate and clump together, forming huge “nets”, among which leukocytes lie “lifeless”, ceasing to perform their protective (immune) functions.
In parallel with this, the functioning of all excretory organs and systems deteriorates. Increasing acidosis is inhibited by the body using a second buffer system. Acids are neutralized by alkaline earth metals and other minerals. Potassium, sodium, magnesium, and calcium replace hydrogen in acids and form neutral salts. The resulting salts should be excreted through the kidneys, but as a result of blood overoxidation, sludge and impaired microcirculation, they are not completely eliminated and are stored inside the body and, above all, inside the connective, least differentiated tissue, which is subject to the greatest destruction. The more acidified the blood becomes, the fewer salts can be dissolved in it and, accordingly, the greater their amount is deposited throughout the body.
Against the background of tissue hypoxia, acidosis and constant loss of minerals, free radicals are “activated”. The body cannot cope with their “destruction” on its own, and they turn on “nuclear reactions” of cell disintegration, causing irreparable damage to them. Under an electron microscope, sick people can detect a huge number of red blood cells “bitten” by free radicals, resembling clock gears. The number of such red blood cells can reach up to 50%. It is clear that this situation aggravates the general condition of a person and brings it to critical condition.
The main components of metabolism (homeostasis) are water, electrolyte and acid-base balance. In a healthy person they should be in biological balance. All of them are extremely important for human health and life.
I have already written a lot of material about water balance on this site and I will not repeat myself, I will only say that chronic lack of drinking clean water (involuntary chronic dehydration) is the background against which metabolic processes take place. It is chronic thirst that contributes to the increase in tissue acidosis, coupled with which, the nutritional intake of acid-forming foods destroys minerals necessary for life and activates free radicals. Essentially, involuntary chronic dehydration is the trigger for the appearance of all kinds of symptoms caused by a malfunction of two other parts of homeostasis.
Restoring a disturbed metabolism is impossible without correcting its basic functions (links). For the concept of health, understanding the importance of good water is paramount!
It is the quality and required volume of drinking water that ensures the normal course of biochemical reactions. The quality of water depends on its pH, oxidation-reduction potential (ORP) and, of course, on its hardness and mineral composition. I don’t want to list a bunch of negative factors that make water unacceptable for drinking, since we are talking about filtered, pure spring or artesian water.
Since as a result of poor nutrition, many different acids are often formed in the body, which can cause burns to tissues (cells), it is necessary to neutralize them with the help of alkaline drinking or free mineral ions supplied with food or water. Unfortunately, this most often does not happen and the acids begin to “gut” the tissues, pulling out minerals from them to replace hydrogen in the acids.
Neutral salts are formed and the level of blood acidity decreases. Hard water usually contains a lot of calcium and magnesium salts, which, when entering the body, aggravate the human condition due to the already high concentration of salts formed during the neutralization of acids. Hard water increases the amount of toxins, especially in people who constantly consume acid-forming foods. Osteoporosis is largely a consequence of calcium loss due to the high acidity of body fluids. Calcium released from the bones actively neutralizes acids, forming salts and clogging the kidneys with them (urolithiasis) and at the same time, when its molecular bonds are broken, it gives the body additional energy.
Of great importance for the fight against acidosis, in addition to correct thinking regarding your diet and reducing the intake of acid-forming foods into the body, is the functional state of the kidneys and lungs. The lion's share of all acids and salts (metabolites) dissolved in the blood and filtered through them is excreted through the kidneys, and through the lungs, thanks to gas exchange, volatile gaseous toxins are released before they have yet formed toxic acids, in particular carbon dioxide (in essence, this is almost ready-made carbon dioxide).
Poor kidney function, pulmonary pathology and smog in the surrounding atmosphere themselves cause acidosis. If we add to this all of the above, it becomes clear how difficult it is for the body to resist the endogenous acid threat, which is rapidly burning the health and life of a particular person.
A kind of vicious circle arises when a violation of metabolic processes leads to acidosis, acidosis affects the excretory organs, gradually limiting their functions, which in turn aggravates acid processes in the body, which continue to have an even more severe impact on the activity of internal organs and systems. All this contributes to further disruption of metabolic processes in a living cell (disturbance in the production of enzymes) and the production of hormones in the endocrine glands, which in turn leads to very serious consequences. One link of violations leads to another, and in order to break this vicious circle, a person must make certain efforts to orient himself in the right direction, to begin to act, without turning his restructuring into a short-term action. Actions aimed at changing the situation towards health must be reasonable, systematic and constant. This is the only way a person can get out of a difficult situation.
The longer symptomatic treatment is applied to an organism damaged as a result of dehydration and acidosis, the faster healthy cells suffocate and die prematurely from continuously accumulating toxins and wastes. Any medications prescribed by doctors or taken at your own risk only increase cell oppression. And the stress and fears of illness experienced by such people finally finish them off. Lack of energy, weakness, laziness and apathy lead to depression. Chronic fatigue syndrome, which doctors give us as a diagnosis, is a consequence of a state of chronic dehydration and acidosis.
There can only be one way out here. Understand what is happening to you by carefully studying what is written about not only in this article but also in other materials on this blog and begin to implement simple but vital recommendations. Don't get me wrong, few doctors can guide you on the right path. At best, while prescribing medications, you may be advised to drink water, but even then they will not tell you how to do it.
I know how to solve the main components of metabolism (homeostasis). Water, electrolyte and acid-base balances can be easily adjusted using portable structurers - alkaline energy glasses - ionizers.
You can get to know them . By the way For the Day of Knowledge, I am planning an unprecedented promotion, thanks to which you will be able to get structurers at a magical price, along with gifts that, without any doubt, will greatly delight you.
The quantity of goods in stock is small, so in order to take advantage of the favorable situation, I recommend signing up for the preliminary list of potential customers.
Call me at the phone number listed on the main page in the upper right corner of this site. Or register in writing by clicking on the picture below. You will be the first to be notified about the start of the promotion.
Signing up for the preliminary list does not oblige you to anything, you just tell me about yourself and your intentions. Only after the announcement of the promotion, you will be able to make an official order by following special links.
Follow the advertisement about the start of the promotion here on the website
Best wishes, your Doctor BIS
PS: Don't waste days so you don't waste years. Real maintenance and regulation of the internal environment is almost free. You will always be able to control your internal environment even if you are not too dependent on nutrition. Don't miss your chance to get a structurer at a discount and great gifts.
PPS: Still haven’t figured out what’s what? Subscribe to the newsletter and receive a series of letters and 4 books on this topic. There is only one life - take care of it!
5167 0
The acid-base state (ABS) is one of the very important components of the body’s homeostasis, an indispensable condition for the optimal activity of enzyme catalysts for metabolic processes. During the metabolic process, various acids and bases are formed, and they are also introduced from the outside. Disorders of various organs can lead to disruption of CBS, which in turn causes various pathological changes in the body. In some cases, KOS indicators are a fairly accurate criterion of IT efficiency. Therefore, it is necessary to know the mechanisms of physiological regulation and disorders of CBS, be able to assess their condition and correctly carry out the prevention and correction of disorders.
Diagnostics
The values of the CBS indicators are maintained within narrow limits by physico-chemical reactions and neurohumoral mechanisms of powerful systems:
- buffer (hemoglobin, protein, bicarbonate, etc.)
- functional (lungs, kidneys, liver, gastrointestinal tract).
When the pH changes, the body's buffer systems immediately react, then the functional ones. The maximum compensation of the latter is slower (lungs - about 12-24 hours, kidneys - about a week). Therefore, to assess the CBS, you need to know the qualitative and quantitative changes primarily in buffer systems (especially hemoglobin, which accounts for 73-76% of the total buffer capacity of the blood, and bicarbonate, which is very mobile and reflects the state of other buffer systems). The main indicators of KOS: pHa - current pH, BEa - excess bases, PaCO2 - CO2 tension in arterial blood at a temperature of 38 ° C without air access.
Normal pH values in humans are 7.36-7.44. The limits of pathological deviations compatible with life are 6.8-8.0. A decrease in pH indicates acidemia, and an increase indicates alkalemia. The conditions that lead to them are called acidosis or alkalosis. pH reflects the degree of compensation, but not the essence of CBS shifts.
Normal values are BEa±2.3 mmol/l. In pathology, the value of BEa can vary within ±15 mmol/l. BEA is a metabolic component of CBS; a decrease or increase in it indicates metabolic acidosis or alkalosis, respectively. BE can also change compensatory for respiratory disorders.
The acid-base state is one of the most important physical and chemical parameters of the internal environment of the body. In the body of a healthy person, acids are constantly formed daily during the metabolic process - about 20,000 mmol of carbonic acid (H 2 C0 3) and 80 mmol of strong acids, but the concentration of H + fluctuates in a relatively narrow range. Normally, the pH of the extracellular fluid is 7.35-7.45 (45-35 nmol/l), and the pH of the intracellular fluid is on average 6.9. At the same time, it should be noted that the H+ concentration inside the cell is heterogeneous: it is different in the organelles of the same cell.
H+ are reactive to such an extent that even a short-term change in their concentration in the cell can significantly affect the activity of enzyme systems and physiological processes; however, normally, buffer systems instantly turn on, protecting the cell from unfavorable pH fluctuations. The buffer system can bind, or, conversely, release H+ immediately in response to changes in the acidity of the intracellular fluid. Buffer systems also operate at the level of the body as a whole, but ultimately the regulation of the body’s pH is determined by the functioning of the lungs and kidneys.
So, what is the acid-base state (syn.: acid-base balance; acid-base state; acid-base balance; acid-base homeostasis)? This is the relative constancy of the pH value of the internal environment of the body, due to the combined action of buffer and some physiological systems of the body.
Acid-base balance is the relative constancy of the hydrogen index (pH) of the internal country of the body, due to the combined action of buffer and some physiological systems, which determines the usefulness of metabolic transformations in the cells of the body (Big Medical Encyclopedia, vol. 10, p. 336).
The ratio of hydrogen and hydroxyl ions in the internal environment of the body depends on:
1) enzyme activity and intensity of redox reactions;
2) processes of hydrolysis and protein synthesis, glycolysis and oxidation of carbohydrates and fats;
3) sensitivity of receptors to mediators;
4) membrane permeability;
5) the ability of hemoglobin to bind oxygen and release it to tissues;
6) physicochemical characteristics of colloids and intercellular structures: the degree of their dispersity, hydrophilia, adsorption ability;
7) functions of various organs and systems.
The ratio of H+ and OH- in biological media depends on the content of acids (proton donors) and buffer bases (proton acceptors) in body fluids. The active reaction of the medium is assessed by one of the ions (H+ or OH-), most often by H+. The H+ content in the body depends on their formation during the metabolism of proteins, fats and carbohydrates, as well as their entry into the body or removal from it in the form of non-volatile acids or carbon dioxide.
The pH value, which characterizes the state of the CBS, is one of the most “hard” blood parameters and varies in humans within very narrow limits: from 7.35 to 7.45. A pH shift of 0.1 beyond the specified limits causes pronounced disturbances in the respiratory, cardiovascular system, etc., a pH decrease of 0.3 causes acidotic coma, and a pH shift of 0.4 is often incompatible with life.
The exchange of acids and bases in the body is closely related to the exchange of water and electrolytes. All these types of metabolism are united by the law of electrical neutrality, isosmolarity and homeosgatic physiological mechanisms.
The total amount of plasma cations is 155 mmol/l (Na+ -142 mmol/l; K+ - 5 mmol/l; Ca2+ - 2.5 mmol/l; Mg2+ - 0.5 mmol/l; other elements - 1.5 mmol/l ) and the same amount of anions is contained (103 mmol/l - weak base Cl-; 27 mmol/l - strong base HC03-; 7.5-9 mmol/l - protein anions; 1.5 mmol/l - phosphate anions; 0. 5 mmol/l - sulfatanions; 5 mmol/l - organic acids). Since the H+ content in plasma does not exceed 40x106 mmol/l, and the main buffer bases of plasma HCO3- and protein anions are about 42 mmol/l, the blood is considered a well-buffered medium and has a slightly alkaline reaction.
Protein and HCO3- anions are closely related to the metabolism of electrolytes and CBS. In this regard, the correct interpretation of changes in their concentration is of decisive importance for assessing the processes occurring in the exchange of electrolytes, water and H+. CBS is supported by blood and tissue buffer systems and physiological regulatory mechanisms, which involve the lungs, kidneys, liver, and gastrointestinal tract.
Physicochemical homeostatic mechanisms
Physicochemical homeostatic mechanisms include buffer systems of blood and tissues and, in particular, the carbonate buffer system. When the body is exposed to disturbing factors (acids, alkalis), the maintenance of acid-base homeostasis is ensured, first of all, by a carbonate buffer system consisting of weak carbonic acid (H 2 CO3) and the sodium salt of its anion (NaHCO3) in a ratio of 1:20. When this buffer comes into contact with acids, the latter are neutralized by the alkaline component of the buffer with the formation of weak carbonic acid: NaHC03 + HCl > NaCl + H2C03
Carbonic acid dissociates into CO2 and H20. The resulting CO2 excites the respiratory center, and excess carbon dioxide is removed from the blood with exhaled air. The carbonate buffer is also able to neutralize excess bases by binding with carbonic acid to form NaHCO3 and its subsequent excretion by the kidneys:
NaOH + H2C03 > NaHCO + H20.
The specific gravity of the carbonate buffer is small and amounts to 7-9% of the total buffer capacity of the blood, however, this buffer occupies a central place in its importance in the blood buffer system, since it is the first to come into contact with disturbing factors and is closely connected with other buffer systems and physiological regulatory mechanisms. Therefore, the carbonate buffer system is a sensitive indicator of CBS, so the determination of its components is widely used to diagnose CBS disorders.
The second buffer system of the blood plasma is a phosphate buffer formed by monobasic (weak acids) and dibasic (strong bases) phosphate salts: NaH2P04 and Na2HP04 in a ratio of 1:4. Phosphate buffer acts similarly to carbonate buffer. The stabilizing role of phosphate buffer in the blood is insignificant; it plays a much greater role in the renal regulation of acid-base homeostasis, as well as in the regulation of the active reaction of some tissues. The phosphate buffer in the blood plays an important role in maintaining the ACR and the reproduction of the bicarbonate buffer:
H2CO3 + Na2HPO4 > NaHC03 + NaH2PO 4 i.e. excess H2C03 is eliminated, and the concentration of NaHC03 increases, and the ratio of H2C03/NaHC03 remains constant at 1:20.
The third blood buffer system is proteins, the buffering properties of which are determined by their amphotericity. They can dissociate to form both H+ and OH-. However, the buffering capacity of plasma proteins compared to bicarbonates is small. The largest buffering capacity of blood (up to 75%) is hemoglobin. Histidine, which is part of hemoglobin, contains both acidic (COOH) and basic (NH2) groups.
The buffering properties of hemoglobin are due to the possibility of interaction of acids with the potassium salt of hemoglobin to form an equivalent amount of the corresponding potassium salt and free hemoglobin, which has the properties of a very weak organic acid. Large amounts of H+ can be bound in this way. The ability to bind H+ in Hb salts is more pronounced than in oxyhemoglobin salts (HbO2). In other words, hemoglobin is a weaker organic acid than oxyhemoglobin. In this regard, during the dissociation of HbO, an additional amount of bases (Hb salts) appear in the tissue capillaries on O2 and Hb, capable of binding carbon dioxide, counteracting the decrease in pH, and vice versa, the oxygenation of Hb leads to the displacement of H2CO3 from bicarbonate. These mechanisms operate during the conversion of arterial blood into venous blood and vice versa, as well as when pCO2 changes.
Hemoglobin is able to bind carbon dioxide using free amino groups, forming carbohemoglobin
R-NH2 + CO2 - R-NHCOOH
Thus, NHC03 in the carbonate buffer system during the “aggression” of acids is compensated by alkaline proteins, phosphates and hemoglobin salts.
The exchange of Cl and HCO3 between erythrocytes and plasma is extremely important in maintaining CBS. With an increase in the concentration of carbon dioxide in the plasma, the concentration of Cl in it decreases, since chlorine ions pass into red blood cells. The main source of Cl in plasma is NaCl. As the concentration of H2CO3 increases, the bond between Na+ and Cl- breaks and their separation occurs, with chlorine ions entering the erythrocytes, and sodium ions remaining in the plasma, since the erythrocyte membrane is practically impermeable to them. At the same time, the resulting excess Na+ combines with excess HCO3-, forming sodium bicarbonate and replenishing its loss during blood acidification and thus maintaining a constant blood pH.
A decrease in pCO2 in the blood causes the opposite process: chlorine ions leave the red blood cells and combine with excess sodium ions released from NaHC03, which prevents alkalization of the blood.
An important role in maintaining CBS belongs to tissue buffer systems - they contain carbonate and phosphate buffer systems. However, a special role is played by tissue proteins, which have the ability to bind very large quantities of acids and alkalis.
An equally important role in the regulation of CBS is played by homeostatic metabolic processes occurring in tissues, especially in the liver, kidneys and muscles. Organic acids, for example, can be oxidized to form volatile acids that are easily released from the body (mainly in the form of carbon dioxide), or combine with products of protein metabolism, completely or partially losing their acidic properties.
Lactic acid, formed in large quantities during intense muscular work, can be resynthesized into glycogen, and ketone bodies into higher fatty acids, and then into fats, etc. Inorganic acids can be neutralized by potassium and sodium salts, released when amino acids are deaminated with ammonia to form ammonium salts.
Alkalies can be neutralized by lactate, which is intensively formed from glycogen when the pH of tissues shifts. CBS is maintained due to the dissolution of strong acids and alkalis in lipids, their binding by various organic substances into non-dissociable and insoluble salts, and the exchange of ions between the cells of various tissues and the blood.
Ultimately, the determining link in maintaining acid-base homeostasis is cellular metabolism, since the transmembrane flow of anions and cations and their distribution between extra- and intracellular sectors is the result of cell activity and is subject to the needs of this activity.
Physiological homeostatic mechanisms
An equally important role in maintaining acid-base homeostasis is played by physiological homeostatic mechanisms, among which the leading role belongs to the lungs and kidney.” Organic acids formed during the metabolic process, or acids that enter the body from the outside, thanks to the buffer systems of the blood, displace carbon dioxide from its compounds with bases, and the resulting excess CO2 is excreted by the lungs.
Carbon dioxide diffuses approximately 20 times more intensely than oxygen. This process is facilitated by two mechanisms:
the transition of hemoglobin to oxyhemoglobin (oxyhemoglobin, as a stronger acid, displaces CO2 from the blood);
The action of pulmonary carbonic anhydrase carbonic anhydrase
n2co3 - co2+ n2o.
The amount of carbon dioxide removed from the body by the lungs depends on the frequency and amplitude of breathing and is determined by the carbon dioxide content in the body.
The participation of the kidneys in maintaining CBS is determined mainly by their acid-excreting function. Under normal conditions, the kidneys produce urine whose pH ranges from 5.0 to 7.0. The pH value of urine can reach 4.5, which indicates an 800-fold excess of H+ in it compared to blood plasma. Acidification of urine in the proximal and distal renal tubules is a consequence of H+ secretion (acidogenesis). An important role in this process is played by carbonic anhydrase of the epithelium of the renal tubules. This enzyme accelerates the achievement of equilibrium between the slow reaction of hydration and dehydration of carbonic acid:
carbonic anhydrase
n2co3 - n2o + co2
As pH decreases, the rate of uncatalyzed H2CO3 > H2 + HCO3- increases. Thanks to acidogenesis, acidic components of the phosphate buffer (H + + HP04 2- > H2PO4-) and weak organic acids (lactic, citric, β-hydroxybutyric, etc.) are removed from the body. The release of H+ by the epithelium of the renal tubules occurs against an electrochemical gradient with energy costs, and at the same time reabsorption of an equivalent amount of Na+ occurs (a decrease in Na+ reabsorption is accompanied by a decrease in acidogenesis). Na+ reabsorbed due to acidogenesis forms sodium bicarbonate in the blood together with HCO3- secreted by the epithelium of the renal tubules
Na + + HC03 - > NaHC03
H+ ions secreted by the epithelium of the renal tubules interact with the anions of buffer compounds. Acidogenesis ensures the release of predominantly anions of carbonate and phosphate buffers and anions of weak organic acids.
Anions of strong organic and inorganic acids (CI-, S0 4 2-) are removed from the body by the kidneys due to ammoniogenesis, which ensures the excretion of acids and protects the urine pH from decreasing below the critical level of the distal tubules and collecting ducts. NH3, formed in the epithelium of the renal tubules during the deamination of glutamine (60%) and other amino acids (40%), entering the lumen of the tubules, combines with H+ formed during acidogenesis. Thus, ammonia binds hydrogen ions and removes the anions of strong acids in the form of ammonium salts.
Ammoniogenesis is closely related to acidogenesis, therefore the concentration of ammonium in the urine is directly dependent on the concentration of H+ in it: acidification of the blood, accompanied by a decrease in the pH of the tubular fluid, promotes the diffusion of ammonia from the cells. Ammonium excretion is also determined by the rate of its production and the rate of urine flow.
Chlorides play an important role in the regulation of acid excretion by the kidneys - an increase in HCO3- reabsorption is accompanied by an increase in chloride reabsorption. The chloride ion passively follows the sodium cation. The change in chloride transport is a consequence of the primary change in the secretion of H+ ions and the reabsorption of HCO3 and is due to the need to maintain the electrical neutrality of tubular urine.
In addition to acidosis and ammoniogenesis, a significant role in the preservation of Na+ during acidification of the blood belongs to the secretion of potassium. Potassium, released from cells when the pH of the blood decreases, is intensively excreted by the epithelium of the renal tubules while simultaneously increasing the reabsorption of Na+ - this affects the regulatory effect of mineralocorticoids: aldosterone and deoxycorticosterone. Normally, the kidneys secrete predominantly acidic metabolic products, but with an increased intake of bases into the body, the urine reaction becomes more alkaline due to the increased secretion of bicarbonate and basic phosphate.
The gastrointestinal tract plays an important role in the excretory regulation of CBS. Hydrochloric acid is formed in the stomach: H+ is secreted by the gastric epithelium, and CI- comes from the blood. In exchange for chlorides, bicarbonate enters the blood during gastric secretion, but alkalization of the blood does not occur, since the CI- gastric juice is reabsorbed into the blood. In the intestine, the epithelium of the intestinal mucosa secretes alkaline juice rich in bicarbonates. In this case, H+ passes into the blood in the form of HCl. A short-term shift in the reaction is immediately balanced by the reabsorption of NaHC03 in the intestine. The intestinal tract, in contrast to the kidneys, which concentrate and release mainly K+ and monovalent cations from the body, concentrates and removes divalent alkaline ions from the body. With an acidic diet, the release of mainly Ca2+ and Mg2+ increases, and with an alkaline diet, the release of all cations increases.
