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  • Title: Na+/H+ antiporter of brush border vesicles: studies with acridine orange uptake.
    Author: Warnock DG, Reenstra WW, Yee VJ.
    Journal: Am J Physiol; 1982 Jun; 242(6):F733-9. PubMed ID: 6283903.
    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.
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