title: Proton gradients in renal cortex brush-border membrane vesicles. Demonstration of a rheogenic proton flux with acridine orange.
abstract: The fluorescence quenching of acridine orange has been used to study the formation and dissipation of acid interior pH gradients in brush-border membrane vesicles from rabbit renal cortex. Acidic interior pH gradients were produced by 1) outwardly directed gradients of Na+ or K+, and 2) the addition of vesicles equilibrated at pH 6.0 to 7.5 buffer. The rate of pH gradient dissipation was stimulated 6.3-fold by the replacement of tetramethylammonium gluconate by tetramethylammonium chloride. A further increase, of 2-fold, was seen upon the addition of carbonyl cyanide-m-chlorophenylhydrazine, demonstrating the existence of a Cl- conductance pathway. In the presence of valinomycin, the replacement of tetramethylammonium gluconate by K gluconate increased the rate of delta pH dissipation by 11-fold, demonstrating the existence of a conductive pathway for protons. This pathway for protons was also shown by the formation of an acidic interior space by an outwardly directed K gradient in the presence of valinomycin. The parallel conductive pathways for H+ and Cl- may dissipate pH and chloride gradients across the luminal membrane of the proximal tubule.
mesh_terms: D000165:Acridine Orange; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D005260:Female; D006863:Hydrogen-Ion Concentration; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D002712:Chlorides; D014634:Valinomycin; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D012964:Sodium; D000165:Acridine Orange; D011188:Potassium