Na+ and K+ fluxes stimulated by Na+-coupled glucose transport: Evidence for a Ba2+-insensitive K+ efflux pathway in rabbit proximal tubules

Abstract

Addition of glucose or the nonmetabolizable analogue α-methyl-d-glucoside to rabbit proximal tubules suspended in a glucoseand alanine-free buffer caused a sustained increase in intracellular Na⁺ content (+43±7 nmol · (mg protein)⁻¹) and a concomitant but larger decrease in K⁺ content (−72±11 nmol· (mg protein)⁻¹). A component of the net K⁺ efflux was Ba²⁺ insensitive, and was inhibited by high (1mm) but not low (10 μm) concentrations of the diuretics, furosemide and bumetanide. The increase in intracellular Na⁺ content is consistent with the view that the increased rates of Na⁺ and water transport seen in the proximal tubule in the presence of glucose can be attributed (at least in part) to a stimulation of basolateral pump activity by an increased [Na⁺] _i .