| 单词 | histamine | |||
| 释义 | histaminehis·ta·mineH0217200 (hĭs′tə-mēn′, -mĭn)histamine(ˈhɪstəˌmiːn; -mɪn)his•ta•mine(ˈhɪs təˌmin, -mɪn)n. his·ta·mine(hĭs′tə-mēn′)histamine
histaminehistamine(hĭs`təmēn'), organic compound derived in the body from the amino acid histidinehistidine, organic compound, one of the 22 α-amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein. ..... Click the link for more information. by the removal of a carboxyl group (COOH). Although found in many plant and animal tissues, histamine is specifically important in human physiology because it is one of the chemicals released from certain cells (particularly mast cells) upon tissue injury or during the neutralization of foreign material (antigens) by certain types of antibodies. Released histamine tends to dilate blood capillaries, often causing the skin to appear red and feel warm, and makes the capillaries more permeable, allowing fluid to escape into the tissues. This causes edema (swelling), usually manifested as acute urticaria (rapidly appearing hives, accompanied by severe itching). This sort of reaction is common to many allergies, such as food allergies, and the symptoms can often be controlled well with antihistaminesantihistamine , any one of a group of compounds having various chemical structures and characterized by the ability to antagonize the effects of histamine. Their principal use in medicine is in the control of allergies such as hay fever and hives. ..... Click the link for more information. . Unfortunately, histamine is not the only substance released under these conditions, and some allergies, particularly chronic ones such as asthma, are relatively resistant to antihistamine therapy. HistamineA biologically active amine that is formed by the decarboxylation of the amino acid histidine. It is widely distributed in nature and is found in plant and animal tissues as well as in insect venoms. In humans, histamine is a mediator of inflammatory reactions, and it functions as a stimulant of hydrochloric acid secretion in the stomach. Most tissue histamine is found stored in mast cells, where it can be released by a variety of stimuli. Once released, it can cause many effects, including constriction of bronchiolar, gastrointestinal, uterine smooth muscle, and lowering of blood pressure. If histamine is released in the skin, itching, a flare (area of redness) due to vasodilation, and a wheal due to leaking of fluid into the tissue are observed. The increase in vascular permeability that permits this leakage is due to an action on the endothelial cells of postcapillary venules. All of these actions of histamine are mediated by the activation of histamine receptors, designated either H-1 or H-2. Antihistamine drugs exert their effects by blocking the combination of histamine with these receptors. See Antihistamine Histamine release can be caused by tissue injury, by physical stimuli such as cold or pressure, by drugs such as heroin, and most importantly by immunologic mechanisms. Mast cells in the skin, the lung, the nasal passages, or other sites may become sensitized to antigens such as ragweed or other pollens, and then release histamine and other biologically active substances upon exposure to them. The released histamine may then cause the effects commonly associated with allergic responses. If the allergic reaction becomes generalized and severe, life-threatening anaphylactic shock may ensue. The prompt administration of epinephrine, which exerts effects opposite to those of histamine, can be life-saving in such cases. See Allergy, Antigen, Epinephrine, Hypersensitivity, Immunology Histamine[β-imidazole-4(5)-ethylamine], a tissue hormone that is strongly biologically active; one of the biogenic amines. It is formed as a result of the decarboxylation of the amino acid, histidine:
Histamine is contained in large quantities in inactive, bound form in various organs and tissues of animals and humans (lungs, liver, and skin), and also in thrombocytes and leucocytes. It is liberated in cases of anaphylactic shock and inflammatory and allergic reactions. It produces dilation of the capillaries and an increase in their permeability, constriction of the large vessels, contraction of the smooth musculature, and sharp increase of hydrochloric-acid secretion in the stomach. The release of histamine from its bound state during allergic reactions leads to reddening of the skin, itching, burning, and formation of blisters. Histamine decomposes under the action of the enzyme histaminase, mainly in the intestinal tract and the kidneys. Histaminase (diaminoxidase) catalyzes the oxidative deamination of histamine, as a result of which a nontoxic product (imidazole-acetaldehyde) is formed. The enzyme is active only in the presence of oxygen; it may deaminate diamines other than histamine. E. V. PETUSHKOVA histamine[′his·tə‚mēn]histaminehistaminehistamine[his´tah-mēn]There are three types of cellular receptors" >histamine receptors : H1 receptors mediate contraction of smooth muscle and capillary dilation, and H2 receptors mediate acceleration of heart rate and promotion of gastric acid secretion. Both types mediate contraction of vascular smooth muscle. H3 receptors occur in a number of systems including the central nervous system and peripheral nerves, and are believed to play a role in regulation of the release of histamine and other neurotransmitters from neurons. Histamine is used as a diagnostic aid in testing gastric secretion and in the diagnosis of pheochromocytoma. An excess of histamine apparently is released when the body comes in contact with certain substances to which it is sensitive. This excess histamine is believed to be the final cause of hay fever, urticaria (hives), and most other allergies, as well as certain stomach upsets and some headaches. There are two types of histamine antagonists in clinical use that act at either the H1 or the H2 receptors. Drugs such as diphenhydramine (Benadryl) and chlorpheniramine(Chlor-Trimeton) are referred to as antihistamines and act on the H1 receptors; they block the effects of histamine on vascular, bronchial, and gastrointestinal smooth muscle and on capillary permeability. They are used for relief of allergic and gastrointestinal disorders and in over-the-counter cold medicines. Drugs such as cimetidine(Tagamet) act at the H2 receptors and block stimulation of gastric acid secretion. his·ta·mine (H),(his'tă-mēn),histamine(hĭs′tə-mēn′, -mĭn)histamineA bioactive amine and neurotransmitter produced by decarboxylation of histidine, which is stored in mast cells and basophils, and secreted by monocytes, neural, and endocrine cells.Physiology Histamine is a potent mediator of immediate hypersensitivity reactions, and evokes a range of responses—bronchoconstriction, vasodilation, hypotension, tachycardia, flushing, headache, increased vascular permeability and secretion by nasal and bronchial mucous glands. Pathophysiology Histamine causes the symptoms of hay fever, including urticaria, angioedema, and bronchospasm in anaphylactic reactions. Specimen Blood collected in gray-top tube, urine Ref range 5–15 µg/dL serum; 0–118 µg/24 hours, urine. Method Fluorometry—blood; ELISA—urine; activation of H2 receptors alone increased gastric acid secretion NEJM 1994; 330:1663rv; histamine acts via histamine (H1, H2, and H3) receptors; allergic responses to inflammation include smooth muscle contraction in the respiratory and GI tracts, and release of nitric oxide from vascular endothelium, stimulating guanylate cyclase and increased levels of cGMP. histamineAllergy medicine A bioactive amine/neurotransmitter produced by decarboxylation of histidine, stored in mast cells and basophils, and secreted by monocytes, neural, and endocrine cells; it is a potent mediator of immediate hypersensitivity reactions, and evokes a range of responses–bronchoconstriction, vasodilation, hypotension, tachycardia, flushing, headache, ↑ vascular permeability and secretion by nasal and bronchial mucous glands; it is responsible for Sx of hay fever, urticaria, angioedema, and bronchospasm in anaphylaxis. Cf Antihistamines.his·ta·mine(his'tă-mēn)histamineA powerful hormone synthesized and stored in MAST CELLS and basophil cells from which it is released when antibodies attached to the cells are contacted by ALLERGENS such as pollens. Free histamine acts on H1 receptors to cause small blood vessels to widen (dilate) and become more permeable to protein, resulting in the effects known an allergic reactions. It causes smooth muscle cells to contract. Histamine also acts on receptors in the stomach (H2 receptors) to promote the secretion of acid. H2 receptor blockers, such as cimetidine and ranitidine (Zantac) are widely used to control acid secretion.histaminea chemical (C5H9N3) produced by LEUCOCYTES and other cells (e.g. MAST CELLS) that causes blood capillaries to become more permeable and so lose fluids into the tissues, producing a local swelling. Histamines are released when foreign ANTIGENS are present. See ANAPHYLAXIS, IMMUNE RESPONSE.Histaminehis·ta·mine(his'tă-mēn)histamine
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