SCH 28080 is a more selective inhibitor than SCH 32651 at the K+ site of gastric K+/H+-ATPase.

The anti-secretory agents SCH 32651 and SCH 28080 were compared for their potency to interact with the K+ site of guinea-pig parietal cell K+/H+-ATPase and dog kidney Na+/K+-ATPase. SCH 32651 and SCH 28080 had an inhibition constant of 9.0 and 0.02 mumol/l, respectively, for the K+/H+-ATPase. The Ki values for the Na+/K+-ATPase were 140 and 220 mumol/l. The data show that both drugs have a higher affinity to the K+ site of the K+/H+-ATPase than to that of the Na+/K+-ATPase and that the affinity ratio of SCH 28080 in favour of K+/H+-ATPase is much greater (11,000) than that of SCH 32651 (15).