Medical term:
histamine
histamine
[his´tah-mēn]an amine, C5H9N3, produced by decarboxylation of histidine, found in all body tissues. It induces capillary dilation (which increases capillary permeability and lowers blood pressure); contraction of most smooth muscle tissue; increased gastric acid secretion; and acceleration of the heart rate. It is also a mediator of immediate hypersensitivity. adj., adj histamin´ic.
There are three types of cellular 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.
There are three types of cellular 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.
histamine phosphate the phosphate salt of histamine, having the same actions as the base; administered by inhalation to test airway hyperresponsiveness in diagnosis of asthma, subcutaneously as a positive control in skin testing for allergy, and as a diagnostic aid to assess production of hydrochloric acid in the stomach.
histamine test
1. a formerly used test in which histamine was injected to stimulate gastric secretion and measure output of gastric acid.
2. a formerly used test for presence of a pheochromocytoma; persons with such a tumor would show first a fall and then a marked rise in blood pressure.
3. a skin prick test used in evaluation of patients with allergies; skin responses to allergens are compared to the response to a histamine wheal.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
his·ta·mine (H),
(his'tă-mēn),A vasodepressor amine derived from histidine by histidine decarboxylase and present in ergot and in animal tissues. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, and a vasodilator (capillaries and arterioles) that causes a fall in blood pressure. Histamine, or a substance indistinguishable in action from it, is liberated in the skin as a result of injury. When injected intradermally in high dilution, it causes the triple response.
Farlex Partner Medical Dictionary © Farlex 2012
histamine
(hĭs′tə-mēn′, -mĭn)n.
A physiologically active amine, C5H9N3, found in plant and animal tissue and released from mast cells as part of an allergic reaction in humans. It stimulates gastric secretion and causes dilation of capillaries, constriction of bronchial smooth muscle, and decreased blood pressure.
his′ta·min′ic (-mĭn′ĭk) adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
histamine
A 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.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
histamine
Allergy 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.McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
his·ta·mine
(his'tă-mēn)A depressor amine derived from histidine and present in ergot and in animal tissues. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle and a vasodilator (capillaries and arterioles) that causes a fall in blood pressure. Histamine is liberated in the skin as a result of injury; when injected intradermally in high dilution, it causes the triple response.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
histamine
A 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.Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
histamine
a 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.Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
Histamine
A physiologically active compound found in plant and animal tissue and released from mast cells as part of an allergic reaction in humans. It stimulates gastric secretion and causes dilation of capillaries, constriction of bronchial smooth muscle, and decreased blood pressure.
Mentioned in: Allergic Rhinitis, Allergies, Allergy Tests, Fish and Shellfish Poisoning, H-2 Blockers
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
his·ta·mine
(his'tă-mēn)Vasodepressor amine present in ergot and in animal tissues. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, and a vasodilator (capillaries and arterioles) that causes a fall in blood pressure.
Medical Dictionary for the Dental Professions © Farlex 2012
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