Characterization of Syrian hamster gastric mucosal H+,K+-ATPase

Employing a simple one-step sucrose gradient fractionation method, gastric mucosal membrane of Syrian hamster was prepared and demonstrated to be specifically enriched in H+,K+-ATPase activity. The preparation is practically devoid of other ATP hydrolyzing activity and contains high K+-stimulated ATPase activity of at least 4-5 fold compared to basal ATPase activity. The H+,K+-ATPase showed hydroxylamine-sensitive phosphorylation and K+-dependent dephosphorylation of the phosphoenzyme, characteristic inhibition by vanadate, omeprazole and SCH 28080, and nigericin-reversible K+-dependent H+-transport--properties characteristic of gastric proton pump. One notable difference with H+,K+-ATPase of other species has been the observation of valinomycin-independent H+ transport in such membrane vesicles. It is proposed that such H+,K+-ATPase-rich hamster gastric mucosal membrane preparation might provide a unique model to study physiological aspects of H+,K+-ATPase function in relation to HCl secretion.