Istamine

Istamine is not a standard term in scientific usage and is typically a misspelling of histamine, a biogenic amine with important roles in immune response, gastric function, and neurotransmission.

Histamine is produced mainly by the decarboxylation of the amino acid histidine, a reaction catalyzed by the enzyme histidine decarboxylase. It is stored in secretory granules of mast cells and basophils, and in other cell types such as enterochromaffin-like cells and certain neurons. Upon release, histamine exerts diverse effects by acting on four histamine receptor subtypes: H1, H2, H3, and H4.

H1 receptors mediate allergic inflammation, vascular permeability, smooth muscle contraction, and pruritus. H2 receptors stimulate gastric acid secretion in the stomach and can modulate immune cell activity. H3 receptors function primarily in the central nervous system to regulate the release of various neurotransmitters. H4 receptors are associated with immune cell chemotaxis and inflammatory responses.

Histamine is rapidly metabolized by enzymes including diamine oxidase and histamine N-methyltransferase, and its actions are tightly regulated to prevent excessive inflammation or acid secretion. Clinically, histamine is central to allergic reactions and anaphylaxis; it is the target of antihistamine drugs that block H1 receptors, and, in gastrointestinal disorders, of H2 receptor antagonists.

Dietary sources can contribute to histamine levels, and some individuals experience histamine intolerance due to reduced enzyme activity. While istamine appears mainly as a misnomer, histamine remains a key biological mediator with wide-ranging physiological and pharmacological significance.