An ATP-driven proton pump in brush-border membranes from rat renal cortex

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Abstract
The rate of ATP hydrolysis in ATP-preloaded plasma membrane vesicles derived from the luminal membrane of renal cortical tubules, and the rate of H+ secretion out of the same vesicles were investigated. Both were inhibited at low temperature, by the action of filipin, an antibiotic that complexes with cholesterol in plasma membranes, and by the action of blockers of mitochondrial Fo hydrogen channels, dicyclohexylcarbodiimide and Dio-9. Valinomycin in the presence of K+ showed a stimulatory effect, the protonophor carbonyl-cyanid-p-trifluormethoxy-phenylhydrazone stimulated the intravesicular ATP hydrolysis and apparently abolished acidification of the extravesccular medium. Lowering of the pH of the extravesicular medium retarded ATP hydrolysis, while readjustment of extra- and intravesicular pH accelerated ATP hydrolysis again. These findings strongly support the assumption that an ATP-driven proton pump is located in the luminal membrane of renal cortical tubules.