H2-receptor blockade and stimulation of histidine decarboxylase.

Abstract

IT has been apparent for some time that the responses of certain tissues to histamine are not blocked by the classical anti-histaminic drugs such as mepyramine or chlorpheniramine. Two types of histamine receptor have been recognized, H1-receptors which are blocked by mepyramine and H2-receptors which are not1. Responses to histamine mediated through interaction with H2-receptors include increases in heart rate, inhibition of uterine contractility and the secretion of acid by the gastric mucosa. Last year Black and his co-workers reported the results of an extensive series of studies characterizing H2-receptors and showed that burimamide, a thiourea derivative of histamine, is a specific H2-receptor antagonist2,3. Burimamide inhibits, for example, the increase in acid secretion evoked by injections of histamine but does not block histamine induced contractions of guinea-pig ileum unless very high doses are used. We report here an unexpected effect on histamine biosynthesis in the rat glandular stomach produced by two H2-receptor antagonists, burimamide and metiamide.