Histamine

histamine /his·ta·mine/ (his´tah-men) 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. There are three types of cellular receptors of histamine. 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 H1 and H2 receptors mediate the contraction of vascular smooth muscle. H3 receptors are believed to play a role in regulation of the release of histamine and other neurotransmitters from neurons. Histamine is used as an aid in the diagnosis of asthma and a positive control in skin testing.histamin´ic

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his·ta·mine (hst-mn, -mn)

n.

A physiologically active depressor amine found in plant and animal tissue, derived from histidine by decarboxylation and released from cells in the immune system as part of an allergic reaction. It is a powerful stimulant of gastric secretion, constrictor of bronchial smooth muscle, and vasodilator.

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hista·minic (-mnk) adj.

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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

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histamine (hisˑ·t·mēn),

n a chemical produced during allergic reactions that promotes vasodilation and gastric secretions.

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histamine (his´tmēn´),

n a compound found in all cells that is produced by the breakdown of histidine. It is released in allergic, inflammatory reactions and causes dilation of capillaries, decreased blood pressure, increased secretion of gastric juice, and constriction of smooth muscles of the bronchi and uterus.

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histamine

an amine, C₅H₉N₃, produced by decarboxylation of histidine, found in all body tissues.

It induces capillary dilatation, 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. There are two types of cellular receptors of histamine: H₁-receptors, which mediate contraction of smooth muscle and capillary dilatation; and H₂-receptors, which mediate acceleration of heart rate and promotion of gastric acid secretion. Both H₁- and H₂-receptors mediate the contraction of vascular smooth muscle. Histamine may also be a neurotransmitter in the central nervous system. It is used as a diagnostic aid in testing gastric secretion and in the diagnosis of pheochromocytoma.

There are two types of histamine antagonists that act at either the H₁- or the H₂-receptors. Drugs such as diphenhydramine and chlorpheniramine are referred to as antihistamines or H₁-blockers; 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. Drugs such as cimetidine (Tagamet) are referred to as H₂-blockers; they block the stimulation of gastric acid secretion and are used to treat gastrointestinal ulceration.

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histamine-containing foods

some food sources, particularly some species of fish, have high levels of histamine; increased levels can also occur from improper storage which permits conversion of histidine to histamine, and an excessive carbohydrate content may promote bacterial growth, fermentation and production of histamine.

histamine-releasing foods

some foods can cause release of histamine from mast cells; these include egg white, shellfish and fish.

histamine shock

manipulation and particularly surgical trauma to large mast cell tumors may lead to decreased blood pressure and persistant bleeding caused by the release of histamine and vasoactive amines.