Histamine

one of the best-known mediators of allergic inflammation; basic biogenic amine, decarboxylation product of amino acid Histidine; in humans in all body tissues, especially in mast cells and basophilic granulocytes, highest concentrations in the lungs.

Its functions are:

1. Dilatation of the capillaries, increase in capillary permeability and drop in blood pressure. # Contractions of the smooth musculature, for example of the bronchial muscles in the lungs. # Induction of increased gastric acidsecretion. # Increase in heart rate.

Histamine is the mediator of the immediate allergic type reaction.

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