Adenylate cyclase of the dog gastric mucosa: stimulation by histamine and inhibition by metiamide.

The activity of the non-stimulated, basal adenylate cyclase of the dog gastric mucosa is reduced by the histamine H2-receptor antagonist metiamide but not by the histamine H1-receptor antagonist mepyramine. Histamine activates the adenylate cyclase only slightly. In the presence of 10(-5) M metiamide a concentration-dependent stimulation of the enzyme by histamine was found. These data indicate that endogenous histamine in dog gastric mucosal homogenate is contributing at least in part to what is measured as "basal" adenylate cyclase activity. This effect is mediated by H2-receptor excitation and in earlier studies has prevented the demonstration of a stimulatory effect of exogenous histamine on this enzyme.