Histamine belongs to the group of biologically active substances that take part in the basic metabolic processes of the body, and in particular the immune response of the body according to the type of allergy. When hyperreacting the body to an external agent, allergic reactions develop, in the development of which one of the leading roles is played by histamine.
- 1 Histamine metabolism in the body
- 2 Biological mechanism of histamine
- 3 The role of histamine in the development of allergic reactions
- 4 Mechanism of the effect of histamine on body cells
- 5 The use of histamine for medical purposes
Histamine metabolism in the body
The main substance forThe formation of histamine is the amino acid histidine that enters the chemical structure of the protein. In various tissues of the body, histidine is contained in more or less quantity and is in an inactive state in the structure of cells called histiocytes.
External factors affecting the body, such as traumatic injuries, thermal damage, allergic agents, including food and medicinal origin, stress reactions, ionizing radiation, promote the release of histamine from mast cells( histiocytes) and its transition into an active form.
In addition to the endogenous histamine synthesized by the body, this substance is found in consumable foods, especially those belonging to the group kept for a long time at a low temperature: hard cheeses, sausages;as well as in alcoholic beverages. A number of products have been called allergic due to their inherent property to stimulate the production of endogenous histamine.
Mechanism of Biological Action of Histamine
Biologically active histamine released from mast cells has systemic and local effects on the body, namely:
- causes spasmodic contraction of the smooth muscle in the bronchial and intestinal walls, which causes diarrhea, intestinal cramps, spastic respiratory failure;
- stimulates the production of the adrenaline stress hormone by the adrenal cortex, stimulating cardiac function( increasing blood pressure and pulse rate);
- stimulation of the secretory function of the digestive and respiratory systems;
- vascular action, manifested by narrowing of blood vessels of large caliber, and expansion of middle and small arteries;
- increase in permeability of the vascular wall and capillary mesh.
Vascular reactions lead to the appearance of such symptoms as swelling of the mucous membranes of the respiratory system, skin with the appearance of small-scaby rashes, hypotension and the accompanying headache and dizziness.
With a massive release of histamine into the bloodstream, a sharp drop in blood pressure may occur, including collapse, accompanied by loss of consciousness, tonic-clonic seizures, vomiting, and involuntary defecation and urination. This condition is referred to as anaphylactic shock and requires resuscitation.
The role of histamine in the development of allergic reactions
An allergic reaction is a complex mechanism of the immune response of an organism to the penetration of a foreign body( antigen) involving cells of the immune system( antibodies).Antigen, and in the case of allergic reactions, the allergen, penetrating for the first time in the body, stimulates the production of antibodies directed at its neutralization and storage of information in the immune memory.
Antibodies have a strict individuality and are responsible for neutralizing a specific type of antibody, and also provide immunological memory of the body.
With repeated antigenic loading, the body produces a large number of antibodies that attach to a specific antigen, forming antigen-antibody complexes with it. These conglomerates have the ability to attach to the mast cells in which histamine is located.
With the massive attachment of immune complexes to the mast cells, they are ruptured, the histamine released from them passes into the active phase and exerts its effect on the body. The degree of severity of histamine exposure is determined by its concentration in the blood plasma. This is the antigenic pathway of allergic reactions. There are also allergic reactions of exogenous type, in particular with the developmental food mechanism:
- intake of products containing a large amount of histamine;
- intake of products that stimulate the release of mast cells from histamine.
Reactions of this type are carried out by affecting mast cells or increasing the concentration of histamine in the blood without the participation of immune complexes.
Mechanism of histamine effect on body cells
Cellular mechanism of histamine exposure is mediated through receptors located on the surface of cells that are chemically compatible with histamine. As a result, they are called histamine receptors. There are several types of such receptors in the body that determine the type of response to the effect of elevated histamine concentrations: the
- group of H1 receptors is located on the surface of smooth muscle cells forming the muscle layer of the wall of blood vessels, intestines, and also on the cells of the nervous system. The effect on this type of receptor determines such allergic manifestations as the bronchial tree times, intestinal plasmas, puffiness, hyperemia and skin rashes. The mechanism of action of atygistamine antiallergic drugs, of which representatives are dimedrol, suprastin and diazolin, consists in the competitive blocking of this group of receptors;
- group of H2-receptors is located on the membranes of secretory cells of the digestive tract, in particular the stomach, responsible for the secretion of hydrochloric acid and enzymes. Drugs that selectively block these receptors have found application in the treatment of hyperacid gastritis and peptic ulcer. To date, several generations of these drugs are used, the main representatives of which are famotidine, cimetidine, roxatidine and others;
- group of H3 receptors are localized on the surface of nerve cells, performing the function of nerve conduction. By acting on them, antihistamines prolong the time of the nerve impulse. Typically, this effect is a side effect for this group of drugs, but sometimes it can be used as the main( as a sedative and hypnotic).This effect should be taken into account when prescribing antihistamines to persons whose work requires increased concentration of attention( driving, control of mechanisms, etc.) due to pronounced drowsiness and reduced attention concentration after taking them. However, to date, antihistamines have been synthesized with minimal or no sedative effect( loratadine, astemizole and others).
Use of histamine for medical purposes
Histamine has found its application and for medical purposes as a medicinal product. It is available in two pharmaceutical forms:
- histamine powder;
- is a solution of histamine with an active substance concentration of 0.1%.
Histamine is used for subcutaneous administration, for the procedure of electrophoresis and in the form of an ointment. Indications for the use of the drug are the following diseases:
- diseases of the musculoskeletal system: polyarthritis, radiculopathy, rheumatism with predominance of articular lesions, inflammation of the brachial plexus;
- allergic diseases: bronchial asthma, allergic reactions like urticaria, in which therapy is carried out gradually increasing house of the drug in order to develop resistance to the effects of histamine in high concentrations.
In the study of the functional state of the secretory function of the stomach( pH-metry), the secretolytic effect of histamine is used. When administered orally, histamine does not affect the operation of the gastrointestinal tract and is not absorbed into the bloodstream through the intestinal wall.
Antidote for histamine - antihistamines in the treatment of allergies:
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