Inhibition of in vitro stimulated gastric acid secretion by a histamine H2-receptor antagonist, metiamide

The effect of a specific histamine H₂-receptor antagonist, metiamide, on gastric acid secretion induced by histamine or pentagastrin was studied in the isolated frog gastric mucosa and the isolated rat stomach. Histamine or pentagastrin approximately doubled acid secretion by the frog gastric mucosa; metiamide markedly inhibited acid secretion induced by these two stimulants. Consistent and significant stimulation of acid secretion by histamine and pentagastrin could be obtained in the isolated rat stomach provided that stomach preparations with initial low basal secretion were selected and that suitable concentrations of stimulants were used. Acid secretion induced by histamine or pentagastrin in these rat stomach preparations was strongly antagonised by metiamide. These results suggest that the basic effect of the H₂-receptor antagonist is exerted directly on the acid secretory mechanisms in the gastric mucosa, although these in vitro findings do not rule out an additional in vivo effect of metiamide on gastric mucosal blood flow.