histamine

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.

[HIST(IDINE) + AMINE.]

A 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 also 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 also Allergy; Antigen; Epinephrine; Hypersensitivity; Immunology.

The amine formed by decarboxylation of the amino acid histidine in the body, also found in small amounts in cheeses, beer, chocolate, sauerkraut, and wines. Excessive release of histamine from mast cells is responsible for many of the symptoms of allergic reactions. It also stimulates secretion of gastric acid, and administration of histamine provides a test for achlorhydria.

Histamine, a chemical derived from the amino acid histidine, has been implicated in a number of disorders. It is a transmitter of nerve impulses secreted by the hypothalamus in the brain. In addition to its function in the nervous system, it is released from body tissues during allergic reactions. Release into the skin causes nettle rash; release in the lungs contributes to asthma. Certain foods, such as chocolate, fish, and strawberries may stimulate immune cells (mast cells) to secrete histamine in sensitized individuals. This may be responsible for some cases of food intolerance.

A compound found in all cells that is produced by the breakdown of histidine. Histamine 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.

For more information on histamine, visit Britannica.com.

An endogenous substance responsible for some allergic responses in the eyes, nose, and skin (e.g. during a bout of hay fever). It is formed in the body from histidine. Histamine is released by mast cells in most tissues during inflammation. It is also secreted by some areas of the hypothalamus and functions as a metabotropic neurotransmitter belonging to the biogenic amines. It acts as a powerful vasodilator and increases the permeability of blood vessels.

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.

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

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Histamine
IUPAC name	2-(1H-imidazol-4-yl)ethanamine
Identifiers
CAS number	51-45-6 Y
PubChem	774
MeSH	Histamine
SMILES	C1=C(NC=N1)CCN
ChemSpider ID	753
Properties
Molecular formula	C5H9N3
Molar mass	111.15 g mol−1
Melting point	83.5 °C (182.3 °F)
Boiling point	209.5 °C (409.1 °F)
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Histamine is a biogenic amine involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter.^[1] Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues. Histamine increases the permeability of the capillaries to white blood cells and other proteins, in order to allow them to engage foreign invaders in the affected tissues.^[2] It is found in virtually all animal body cells.^{[citation needed]}

Contents 1 Properties 2 Synthesis and metabolism 3 Storage and release 4 Mechanism of action 5 Roles in the body 5.1 Sleep regulation 5.2 Suppressive effects 5.3 Erection and sexual function 5.4 Schizophrenia 6 Disorders 7 Nomenclature 8 See also 9 References 10 External links

Properties

Histamine forms colorless hygroscopic crystals that melt at 84°C, and are easily dissolved in water or ethanol, but not in ether. In aqueous solution histamine exists in two tautomeric forms, N^π-H-histamine and N^τ-H-histamine.

Tautomers of histamine

Histamine has two basic centres, namely the aliphatic amino group and whichever nitrogen atom of the imidazole ring does not already have a proton. Under physiological conditions, the aliphatic amino group (having a pK_a around 9.4) will be protonated, whereas the second nitrogen of the imidazole ring (pK_a ≈ 5.8) will not be protonated.^[3] Thus, histamine is normally protonated to a singly-charged cation.

Synthesis and metabolism

Histamine is derived from the decarboxylation of the amino acid histidine, a reaction catalyzed by the enzyme L-histidine decarboxylase. It is a hydrophilic vasoactive amine.

Conversion of histidine to histamine by histidine decarboxylase

Once formed, histamine is either stored or rapidly inactivated. Histamine released into the synapses is broken down by acetaldehyde dehydrogenase. It is the deficiency of this enzyme that triggers an allergic reaction as histamines pool in the synapses. Histamine is broken down by histamine-N-methyltransferase and diamine oxidase. Some forms of foodborne disease, so-called "food poisonings," are due to conversion of histidine into histamine in spoiled food, such as fish.

Storage and release

Mast cells.

Most histamine in the body is generated in granules in mast cells or in white blood cells called basophils. Mast cells are especially numerous at sites of potential injury - the nose, mouth, and feet, internal body surfaces, and blood vessels. Non-mast cell histamine is found in several tissues, including the brain, where it functions as a neurotransmitter. Another important site of histamine storage and release is the enterochromaffin-like (ECL) cell of the stomach.

The most important pathophysiologic mechanism of mast cell and basophil histamine release is immunologic. These cells, if sensitized by IgE antibodies attached to their membranes, degranulate when exposed to the appropriate antigen. Certain amines and alkaloids, including such drugs as morphine, and curare alkaloids, can displace histamine in granules and cause its release. Antibiotics like polymyxin are also found to stimulate histamine release.

Mechanism of action

Histamine exerts its actions by combining with specific cellular histamine receptors. The four histamine receptors that have been discovered are designated H1 through H4.

Type	Location	Function
H1 histamine receptor	Found on smooth muscle, endothelium, and central nervous system tissue	Causes vasodilation, bronchoconstriction, bronchial smooth muscle contraction, separation of endothelial cells (responsible for hives), and pain and itching due to insect stings; the primary receptors involved in allergic rhinitis symptoms and motion sickness.
H2 histamine receptor	Located on parietal cells	Primarily stimulate gastric acid secretion
H3 histamine receptor	Found on central nervous system and to a lesser extent peripheral nervous system tissue	Decreased neurotransmitter release: histamine, acetylcholine, norepinephrine, serotonin
H4 histamine receptor	Found primarily in the basophils and in the bone marrow. It is also found on thymus, small intestine, spleen, and colon.	Plays a role in chemotaxis.

Roles in the body

Sleep regulation

Histamine is released as a neurotransmitter. The cell bodies of neurons which release histamine are found in the posterior hypothalamus, in various tuberomammillary nuclei. From here, these histaminergic neurons project throughout the brain, to the cortex through the medial forebrain bundle. Histaminergic action is known to modulate sleep. Classically, antihistamines (H1 histamine receptor antagonists) produce sleep. Likewise, destruction of histamine releasing neurons, or inhibition of histamine synthesis leads to an inability to maintain vigilance. Finally, H3 receptor antagonists increase wakefulness.

It has been shown that histaminergic cells have the most wakefulness-related firing pattern of any neuronal type thus far recorded. They fire rapidly during waking, fire more slowly during periods of relaxation/tiredness and completely stop firing during REM and NREM (non-REM) sleep. Histaminergic cells can be recorded firing just before an animal shows signs of waking.

Suppressive effects

While histamine has stimulatory effects upon neurons, it also has suppressive ones that protects against the susceptibility to convulsion, drug sensitization, denervation supersensitivity, ischemic lesions and stress.^[4] It has also been suggested that histamine controls the mechanisms by which memories and learning are forgotten.^[5]

Erection and sexual function

Libido loss and erectile failure can occur following histamine (H2) antagonists such as cimetidine and ranitidine.^[6] The injection of histamine into the corpus cavernosum in men with psychogenic impotence produces full or partial erections in 74% of them.^[7] It has been suggested that H2 antagonists may cause sexual difficulties by reducing the uptake of testosterone.^[6]

Schizophrenia

Metabolites of histamine metabolite are increased in the cerebrospinal fluid of schizophrenics while the binding of H(1) receptor binding sites are decreased. Many atypical antipsychotics have the effect of increasing histamine turnover.^[8]

Disorders

As an integral part of the immune system, histamine may be involved in immune system disorders and allergies.

Nomenclature

"H substance" or "substance H" are occasionally used in medical literature for histamine or a hypothetical histamine-like diffusible substance released in allergic reactions of skin and in the responses of tissue to inflammation.

See also

• Scombroid food poisoning
• Histamine antagonist

References

Histamine and Histamine intolerance[1]

1. ^ Marieb, E. (2001). Human anatomy & physiology. San Francisco: Benjamin Cummings. pp. 414. ISBN 0-8053-4989-8. 
2. ^ Di Guiseppe, Maurice; et al. (2003). Nelson Biology 12. Toronto: Thomson Canada Ltd.. p. 473. ISBN 0-17-625987-2. 
3. ^ Paiva T.B., Tominaga M. & Paiva A.C. (1970). Ionization of histamine, N-acetylhistamine, and their iodinated derivatives. J. Med. Chem., 13, 689–692.
4. ^ Yanai K, Tashiro M. (2007). The physiological and pathophysiological roles of neuronal histamine: an insight from human positron emission tomography studies. Pharmacol Ther. 113(1):1-15. PMID 16890992
5. ^ Alvarez EO. (2009). The role of histamine on cognition. Behav Brain Res. 199(2):183-9. PMID 19126417
6. ^ ^{a b} White JM, Rumbold GR. (1988).Behavioural effects of histamine and its antagonists: a review. Psychopharmacology, 95(1):1-14. PMID 3133686
7. ^ Cará AM, Lopes-Martins RA, Antunes E, Nahoum CR, De Nucci G. (1995). The role of histamine in human penile erection. Br J Urol. 75(2):220-4. PMID 7850330
8. ^ Ito C. (2004). The role of the central histaminergic system on schizophrenia. Drug News Perspect. 17(6):383-7. PMID 15334189

External links

• DrugBank EXPT01785

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v • d • e Neurotransmitters Amino Acids 1,4-Butanediol • Alanine • Aspartate • Cycloserine • DMG • GABA • GHB • Glutamate • Glycine • Hypotaurine • Kynurenic Acid (Transtorine) • NAAG (Spaglumic Acid) • NMG (Sarcosine) • Serine • Taurine • TMG (Betaine) Endocannabinoids 2-AG • 2-AGE (Noladin Ether) • AEA (Anandamide) • NADA • OAE (Virodhamine) • Oleamide Gasotransmitters Carbon Monoxide • Hydrogen Sulfide • Nitric Oxide • Nitrous Oxide Monoamines Dopamine • Epinephrine (Adrenaline) • Melatonin • Norepinephrine (Noradrenaline) • Serotonin (5-HT) Neuropeptides See here for more details. Purines Adenosine • ADP • AMP • ATP Trace Amines 3-ITA • 5-MeO-DMT • Bufotenin • DMT • NMT • Octopamine • Phenethylamine • Synephrine • Thyronamine • Tryptamine • Tyramine Others Acetylcholine • Histamine

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Dansk (Danish)
n. - histamin

Nederlands (Dutch)
histamine (medicijn)

Français (French)
n. - histamine

Deutsch (German)
n. - Histamin

Ελληνική (Greek)
n. - (βιολ.) ισταμίνη

Italiano (Italian)
istamina

Português (Portuguese)
n. - histamina (f) (Quím.)

Русский (Russian)
гистамин

Español (Spanish)
n. - histamina

Svenska (Swedish)
n. - histamin (hormon i kroppens vävnader som frigörs vid överkänslighetsreaktioner)

中文（简体）(Chinese (Simplified))
组织胺

中文（繁體）(Chinese (Traditional))
n. - 組織胺

한국어 (Korean)
n. - 히스타민

日本語 (Japanese)
n. - ヒスタミン

العربيه (Arabic)
‏(الاسم) الهستامين, مركب يكون في الارغوت وفي كثير من الانسجه الحيوانيه‏

עברית (Hebrew)
n. - ‮תרכובת המכווצת שרירים ומרחיבה כלי-דם שמשחררים תאים בגוף בעת פציעה, היסטמין‬

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