title: Contraluminal transport of hexoses in the proximal convolution of the rat kidney in situ.
abstract: In order to study contraluminal hexose transport, concentration and time-dependent influx of 3H-2-deoxy-D-glucose from the interstitium into cortical tubular cells has been measured. The influx curves fit to a two parameter kinetics (Km 1.3 +/- 0.2 mmol/l, Jmax 0.67 +/- 0.16 pmol/s X cm) plus an additional diffusion term (with P = 6 X 10(-8) cm2/s) and a distribution ratio extracellular to intracellular amount of 2-deoxy-D-glucose of 1:0.6. Since the extracellular to intracellular free water space as estimated from morphological data was 1:2, one must conclude that glucose has only free access to 1/3 of the cell water. The intracellularly accessible space was augmented when the tubules were preperfused for 10 s with hypotonic saline. Thereby an increase of the compartment into which diffusion occurs was revealed and a final rupture of this intracellular compartment at 1/4 isotonic solutions was observed. Total replacement of ions in the peritubular perfusate by mannitol did not change 2-deoxy-D-glucose influx, indicating that it is Na+-independent. By adding isotonic concentrations of the respective sugars to the capillary perfusate, three degrees of inhibition of 2-deoxy-D-glucose influx could be revealed: strong inhibition by D-glucose, methyl-beta-D-glucoside, D-mannose, 3-O-methyl-D-glucose, 2-deoxy-D-galactose, methyl-beta-D-galactoside and 6-deoxy-D-glucose, moderate inhibition by D-galactose, L-glucose, L-mannose and D-fructose, no or borderline inhibition by methyl alpha-D-glucoside, 2-deoxy-methyl-alpha-D-galactoside, 1-thio-beta-D-glucose, 1-thio-beta-D-galactose, 5-thio-alpha-D-glucose, myo-inositol and mannitol.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D001692:Biological Transport; D002717:Chlormerodrin / Q000494:pharmacology; D003847:Deoxyglucose / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000378:metabolism; D006601:Hexoses / Q000378:metabolism*; D007328:Insulin / Q000627:therapeutic use; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010477:Perfusion; D010693:Phloretin / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D014316:Tritium
chemical_list: D006601:Hexoses; D007328:Insulin; D014316:Tritium; D002717:Chlormerodrin; D003847:Deoxyglucose; D012964:Sodium; D010693:Phloretin