Sugar uptake into brush border vesicles from normal human kidney.
Uptake studies of simple sugars were performed on a membrane fractions containing osmotically active vesicles prepared from normal human kidney cortex. The uptake of D-glucose was found to be sodium-dependent and phlorizin-sensitive. The specificity of the D-glucose transport mechanism is such that it is shared by alpha-methyl-D-glucoside, D-galactose, and 5-thio-D-glucose, while 2-deoxy-D-glucose, 3-O-methyl-D-glucose, D-mannose, and D-fructose show little, if any, affinity. Measurement of the sodium-dependent component of the initial D-glucose uptake as a function of glucose concentration resulted in a curvilinear Scatchard plot, indicating the possibility of cooperative effects, or alternatively, the existence of two (or more) sodium-dependent D-glucose transporters. In the case of two transporters, we estimate that Km congruent to 0.3 mM and Vmax congruent to 2.5 nmol/min per mg of protein for the "high-affinity transporter," and Km approximately 6 mM and Vmax approximately 8 nmol/min per mg of protein for the "low-affinity transporter." These specificity and kinetic properties strongly suggest that the sodium-dependent D-glucose transport mechanism characterized in our studies is localized to the brush border of the proximal tubule.
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006601:Hexoses / Q000378:metabolism*; D006801:Humans; D007672:Kidney Cortex / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D007700:Kinetics; D008757:Methylglucosides / Q000378:metabolism; D010695:Phlorhizin / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013385:Succinate Dehydrogenase / Q000378:metabolism; D014634:Valinomycin / Q000494:pharmacology
D002352:Carrier Proteins; D006601:Hexoses; D008757:Methylglucosides; D014634:Valinomycin; D012964:Sodium; D010695:Phlorhizin; D013385:Succinate Dehydrogenase; D000469:Alkaline Phosphatase; D000251:Adenosine Triphosphatases; D005947:Glucose