CHARACTERIZATION OF SYRIAN-HAMSTER GASTRIC-MUCOSAL H-ATPASE(,K+)

Employing a simple one-step sucrose gradient fractionation method, gas tric 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 h igh K+-stimulated ATPase activity of at least 4-5 fold compared to bas al ATPase activity. The H+,K+-ATPase showed hydroxylamine-sensitive ph osphorylation and K+-dependent dephosphorylation of the phosphoenzyme, characteristic inhibition by vanadate, omeprazole and SCH 28080, and nigericin-reversible K+-dependent H+-transport - properties characteri stic 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 functio n in relation to HCl secretion.