Inhibition of H+K+ATPase by SCH 28080 and SCH 32651

The novel antiulcer agents, SCH 28080 and SCH 32651 were examined for their ability to inhibit the H+K+ ATPase enzyme activity in a preparation of microsomal membranes from rabbit fundic mucosa. SCH 28080 inhibited the isolated enzyme activity with a potency similar to omeprazole, IC50s of 2.5 and 4.0 microM respectively. SCH 32651 was less potent exhibiting an IC50 of 200.0 microM. Both compounds may therefore exert their antisecretory activity via a direct inhibition of the parietal cell H+K+ ATPase.