Histamine synthesis after administration of gastrin and blockade of acid secretion in the rat stomach.
Histidine decarboxylase (HDC) activity in the oxyntic gland and gastric volume were measured in rats treated with tetragastrin, cimetidine or omeprazole. HDC activity was dose dependently activated by not only tetragastrin but also cimetidine and omeprazole treatment. Histamine concentration in the oxyntic gland was reduced, but the amount of histamine in the gastric contents was increased by tetragastrin treatment. In rats premedicated with cimetidine or omeprazole, histamine concentration in the oxyntic gland and the amount of histamine in the gastric contents were not changed by administration of tetragastrin. It was concluded that tetragastrin activated HDC which increased histamine release into the gastric contents. Cimetidine and omeprazole induced the secretion of endogenous gastrin, leading to the activation of HDC.