Description
In humans, histamine (ß-imidazolethylamine or beta-imidazolethylamine) is the most important mediator and is mostly found in the initial phase of an anaphylactic reaction.
Histamine is derived by the enzymatic decarboxylation of histidine. In the organism, histamine is present in nearly all tissues, and it is mainly stored in the metachromatic granules of mast cells and the basophilic leukocytes. Histamine is present in an inactive bound form and is only released as required. Like several other mediators, histamine does not only mediate various clinical symptoms of anaphylaxis but also induces a series of effects which are directed towards a termination of the anaphylactic reaction. The biological action of histamine in tissue is guaranteed by three different surface receptors, i.e. H1, H2 and H3 receptors.
