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Publisher Summary: This chapter highlights the nature of proton movements across the luminal membrane of renal proximal tubule that have been investigated using isolated brush border membrane vesicles, thereby taking advantage of studying the events separated from other parts of the cell-envelope, cell organelles and cellular metabolism, and under defined conditions controlling the composition of the solutions inside and outside the membrane vesicles. It has been assumed that the adenosine triphosphate (ATP) driven pump is inhibited by the buildup of a proton gradient and a transmembranal electrical potential difference. This assumption is supported by the use of a protonophore like carbonylcyanid-ptrifluormethoxy-phenylhydrazon, which overcomes the paralyzation of the ATPase by relieving the retarding electrochemical difference for protons over the membrane. The chapter also presents a comparison of ATP hydrolysis and acidification of the extravesicular medium. The two parameters show a very similar time course suggesting a causal relationship, and supporting the view of the existence of a sodium-independent, primary active proton translocation, as well as a sodium gradient driven proton extrusion over the brush border membranes in renal proximal tubule.
