title: Na+/H+ antiporter of brush border vesicles: studies with acridine orange uptake.
abstract: Fluorescence quenching of acridine orange was used to characterize the generation and collapse of pH gradients by the Na+/H+ antiporter of brush border membrane vesicles prepared from rabbit renal cortex. Quenching was observed when acridine orange, a weak base, was taken up to an acidic intravesicular space. Na+/H+ exchange was examined with both Na+ uptake and efflux studies. Acridine orange fluorescence quenching demonstrated the cation specificity of the Na+/H+ antiporter (i.e., sodium and lithium) and was inhibited by amiloride. Parallel studies with nigericin, a K+/H+ antiporter, demonstrated that acridine orange responded very rapidly to pH gradients. Therefore, acridine orange equilibration was not rate limiting in our studies of the Na+/H+ antiporter. Initial rate measurements were made to obtain kinetic parameters for the Na+/H+ antiporter. In sodium influx studies, the half-maximal rate of acridine orange fluorescence change was obtained with an external sodium concentration of 13.3 +/- 0.5 mM.
mesh_terms: D000165:Acridine Orange / Q000378:metabolism*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism / Q000648:ultrastructure*; D007700:Kinetics; D008433:Mathematics; D008871:Microvilli / Q000378:metabolism; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers; D013050:Spectrometry, Fluorescence
chemical_list: D002352:Carrier Proteins; D005456:Fluorescent Dyes; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D012964:Sodium; D000165:Acridine Orange