Suppression of rabbit kidney histidine decarboxylase activity by endotoxin

¹ Merck Institute for Therapeutic Research, Rahway, New Jersey, and Department of Pathology, New York University School of Medicine, New York City

Previous work has shown that bacterial endotoxins activate an inducible form of histidine decarboxylase present in mammalian tissues. The product of this enzyme, induced histamine, has been postulated to have a circulatory function and to oppose the vasoconstrictor actions of the catecholamines on the small blood vessels. The present experiments show that in kidney of endotoxin-treated rabbits there is an anomalous response, histidine decarboxylase being strongly reduced, not activated. The findings are consistent with the view that suppression of induced histamine synthesis, at a time of markedly increased catecholamine release, might potentiate the actions of these vasoconstrictors on the kidney. This event may be a factor in the early endotoxin-induced changes in the glomerular capillaries which prepares them for the subsequent events of the generalized Shwartzman reaction.