histamine /his·ta·mine/ (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. 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
Histamine
histamine
histamine [his´tah-mēn]
histamine (hisˑ·t
·mēn),
histamine (his´t
mēn´),
histamine
his·ta·mine (h s t -m n , -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. his ta·minic (-mnk) adj. |
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
histamine
[his′təmēn, -min]
Etymology: Gk, histos, tissue; L, amine, ammonia
a compound, found in all cells, that is produced by the breakdown of histidine. It is released in allergic inflammatory reactions. Cellular receptors of histamine include the H1 receptors, which are responsible for the dilation of blood vessels and the contraction of smooth muscle; the H2 receptors, which are responsible for the stimulation of heart rate and gastric secretion; and H3 receptors, which are believed to play a role in regulation of the release of histamine and other neurotransmitters from neurons. H1 and H2 receptors also mediate the contraction of vascular smooth muscle.
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.
histamine (hisˑ·t
·mēn),n a chemical produced during allergic reactions that promotes vasodilation and gastric secretions.
histamine (his´t
mēn´),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.
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.
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.
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.
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