3-O-methyl-D-glucose uptake in isolated rat hepatocytes. Effects of dexamethasone.
We examined the uptake of 3-O-methyl-D-glucose, a nonmetabolizable hexose, by isolated rat hepatocytes. The uptake of 3-O-methyl-D-glucose was linear for 1 min at 22 degrees, and Lineweaver-Burk analysis demonstrated an apparent Km of approximately 6 mM. Cytochalasin B (40 microM) and phloridzin (2 mM) inhibited 3-O-methyl-D-glucose uptake by 88% and 63%, respectively. D-Glucose (20 mM) inhibited the initial rate of 3-O-methyl-D-glucose uptake by 55% (p less than 0.001), whereas L-glucose was without any significant effect. The uptake of 3-O-methyl-D-glucose remained unchanged in the presence of Na+ (0-150 mM) in the incubation medium. After 30 min dexamethasone inhibited glucose uptake (the maximal effect being achieved in a time- and concentration-dependent manner) at 2 microM and 0.5 microM concentrations by 50% and 25%, respectively. Dexamethasone produced a decrease in the Vmax but did not change the Km. Insulin, glucagon, gastric inhibitory polypeptides, and pancreozymin had no effect on 3-O-methyl-D-glucose uptake in isolated hepatocytes. These findings are consistent with the conclusion that 3-O-methyl-D-glucose uptake in isolated rat hepatocytes occurs via a stereospecific, carrier-mediated, facilitated diffusion process. Dexamethasone decreases this process of facilitated diffusion in the isolated hepatocyte.
D019325:3-O-Methylglucose; D000818:Animals; D001693:Biological Transport, Active; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008757:Methylglucosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism
D008757:Methylglucosides; D008759:Methylglycosides; D019325:3-O-Methylglucose; D003907:Dexamethasone; D005947:Glucose