Turnover of the gastric H+,K(+)-adenosine triphosphatase alpha subunit and its effect on inhibition of rat gastric acid secretion.

Background & Aims: The rate of turnover and the effect of inhibition of acid secretion on the turnover of gastric H+,K(+)-adenosine triphosphatase (ATPase) is unknown. The aim of this study was to determine the turnover of the alpha subunit of gastric H+,K(+)-ATPase in rats under control conditions and during inhibition of acid secretion by ranitidine or omeprazole.

Methods: The turnover of the alpha subunit of the ATPase was determined by measuring the loss of incorporated 35S-methionine.

Characterization of proton transport in bone-derived membrane vesicles.

ATP-dependent proton transport in membrane vesicles prepared from the medullary bone of egg-laying hens, a source rich in osteoclasts, was characterized. Proton transport was abolished by bafilomycin A1 (10 nM) and N-ethylmalemide (50 microM), but not by oligomycin (15 micrograms/ml), vanadate (100 microM) or SCH 28080 (100 microM), thereby differentiating this H(+)-ATPase from the F1F0- and phosphorylated-type of ATPases. Preincubation of the membrane vesicles at 0 degrees C for 1 h in the presence of KCl (0.

Characterization of proton transport in bone-derived membrane vesicles.

ATP-dependent proton transport was characterized in membrane vesicles, prepared by differential centrifugation from medullary bone of egg laying hens, a source rich in osteoclasts. The H(+)-ATPase present in this preparation showed the characteristics of a vacuolar H(+)-ATPase in its sensitivity to inhibitors, including bafilomycin A1, its sensitivity to cold treatment and its electrogenic mechanism. There was no evidence for a direct activation of the H(+)-ATPase by anions, including Cl-.

Omeprazole and bafilomycin, two proton pump inhibitors: differentiation of their effects on gastric, kidney and bone H(+)-translocating ATPases.

The effects of omeprazole and bafilomycin on processes dependent on two different types of H(+)-translocating ATPases were compared. A H(+)-ATPase of the E1E2-type, the H+,K(+)-ATPase, was purified from gastric mucosa. Vacuolar type H(+)-ATPases were prepared both from kidney medulla and from osteoclast-containing medullary bone.