Transport of glucose analogues in rat lung.
Uptake of nonmetabolizable glucose analogues was investigated in isolated rat lungs ventilated with 5% CO2 in air and perfused with Krebs-Ringer bicarbonate medium. In some experiments, [5-3H]glucose, methyl(alpha-D-[U-14C]gluco)pyranoside (alpha-MG), 3-O-methyl-D-[U-14C]glucose (3-O-MG), or various inhibitors were added to the initial perfusate to determine glucose utilization by the rate of 3H2O production or to characterize the uptake of glucose analogues. [1,2-3H]polyethylene glycol (PEG) was used as an indicator of the extracellular water space and gave a mean value of 0.35 ml/g tissue; calculated mean intracellular H2O space was 0.48 ml/g tissue. Glucose utilization was 56.4 +/- 6.6 (mean +/- SE, n = 6) mumol . g dry wt-1 . h-1 and decreased by 61% with 3 mM phlorizin. After 1-2 h perfusion, intracellular alpha-MG concentration was 1.4-1.9 times the extracellular concentration. The mean tissue-to-medium ratio (T/M) for alpha-MG decreased by more than 30% in the presence of glucose (5.0 mM), phlorizin (0.5 mM), ouabain (0.5 mM), or the absence of external Na+. Intracellular 3-O-MG concentration did not exceed extracellular concentration during 2 h of perfusion and the mean T/M did not change with any of the inhibitors studied. The results indicate that the nonmetabolizable glucose analogue alpha-MG is accumulated against a concentration gradient by an active Na+-dependent transport process, whereas 3-O-MG is apparently taken up by a different mechanism.
D019325:3-O-Methylglucose; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008757:Methylglucosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D010695:Phlorhizin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D008757:Methylglucosides; D008759:Methylglycosides; D019325:3-O-Methylglucose; C027020:methylglucoside; D010042:Ouabain; D010695:Phlorhizin; D005947:Glucose