Relationship of induced histidine decarboxylase activity and histamine synthesis to shock from stress and from endotoxin

Abstract

The activity of histidine decarboxylase of various mouse tissues is increased by stress, by epinephrine and by endotoxins. Enzyme activity reaches a maximum in about 6 hours following a stimulus and returns essentially to normal within 1 day. In mice given a lethal dose of endotoxin, enzyme activity is at its highest observed level when the animals become moribund. Evidence is presented that the elevated enzyme activites reflect an increased rate of histamine synthesis in the living animal. The hypothesis of a homeostatic relationship between newly synthesized histamine and the catecholamines, which during intense stress can suffer imbalance, affords a reasonable explanation for the events observed in the small blood vessels during development of shock, for the damaging effects of epinephrine in endotoxin-treated animals and for a number of other phenomena related to shock.