Na+-electrochemical potential-mediated transport of D-glucose in renal brush border membrane vesicles

Abstract

The uphill transport of D-glucose in renal brush border membrane vesicles was correlated with the Na+ electrochemical gradient. Each component of the electrochemical potential, the membrane potential or the Na+ chemical gradient, when assayed independently supported the concentrative uptake of the sugar. When the two components were combined the rates of D-glucose uptake were additive. Accumulation of D-glucose as a function of various Na+ gradients, in the absence of a membrane potential, suggests a 1:1 stoichiometry between sugar and Na+ uptake. These findings are consistent with the role of ionic gradients in energizing uphill solute transport and, thus, provide experimental evidence that extends the chemiosmotic theory to the Na+ electrochemical potential-mediated transport of D-glucose in mammalian tissues.