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

Addition of glucose or the nonmetabolizable analogue alpha-methyl-D-glucoside to rabbit proximal tubules suspended in a glucose- and 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 (1 mM) but not low (10 microM) 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.