Significance of Induced Synthesis of Histamine in Physiology and Pathology

Abstract

Histidine decarboxylase can be activated in all tested vascular tissues by stimuli which increase blood flow in the small vessels and may lead to inflammation, shock and altered behavior of the reticuloendothelial system. The product of this adaptive enzyme, induced histamine, may be an intrinsic regulator of the micro-circulatory system which is potentially harmful. In all the cases where increased histidine decarboxylase activity has been observed, and induced histamine has been proposed as the mediator of some change, large amounts of the adrenal steroids can exert opposite effects. The hypothesis that a major mode of action of the adrenal steroids is antagonism of the microvascular effects of induced histamine unifies many of the known actions of these hormones.