Na+-independent D-glucose transport in rabbit renal basolateral membranes.
To define the mechanism by which glucose is transported across the basolateral membrane of the renal proximal tubular cell, we measured D-[14C]glucose uptake in basolateral membrane vesicles from rabbit kidney. Na+-dependent D-glucose transport, demonstrable in brush-border vesicles, could not be demonstrated in basolateral membrane vesicles. In the absence of Na+, the uptake of D-[14C]glucose in basolateral vesicles was more rapid than that of L-[3H]glucose over a concentration range of 1-50 mM. Subtraction of the latter from the former uptakes revealed a saturable process with apparent Km of 9.9 mM and Vmax of 0.80 nmol.mg protein-1.s-1. To characterize the transport component of D-glucose uptake in basolateral vesicles, we measured trans stimulation of 2 mM D-[14C]glucose entry in the absence of Na+. Trans stimulation could be effected by preloading basolateral vesicles with D-glucose, 2-deoxy-D-glucose, or 3-O-methyl-D-glucose, but not with L-glucose or alpha-methyl-D-glucoside. Trans-stimulated D-[14C]glucose uptake was inhibited by 0.1 mM phloretin or cytochalasin B but not phlorizin. In contrast, Na+-dependent D-[14C]glucose transport in brush-border vesicles was inhibited by phlorizin but not phloretin or cytochalasin B. Our findings are consistent with the presence of a Na+-independent D-glucose transporter in the proximal tubular basolateral membrane with characteristics similar to those of transporters present in nonepithelial cells.
Cheung
P T
PT
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Hammerman
M R
MR
D019325:3-O-Methylglucose; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D001693:Biological Transport, Active; D002250:Carbon Radioisotopes; D003571:Cytochalasin B / Q000378:metabolism; D003847:Deoxyglucose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D007536:Isomerism; D007553:Isotope Labeling; D007668:Kidney / Q000648:ultrastructure*; D008757:Methylglucosides / Q000378:metabolism; D010693:Phloretin / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology*; D014316:Tritium
D002250:Carbon Radioisotopes; D008757:Methylglucosides; D014316:Tritium; D019325:3-O-Methylglucose; D003571:Cytochalasin B; D003847:Deoxyglucose; D012964:Sodium; D005947:Glucose; D010693:Phloretin