title: Kinetics of glycerol uptake by the perfused rat liver. Membrane transport, phosphorylation and effect on NAD redox level.
abstract: The kinetics of glycerol uptake by the perfused rat liver were determined according to a model which includes membrane transport, intracellular  phosphorylation and competitive inhibition of glycerol phosphorylation by L-glycerol 3-phosphate. The membrane transport obeys first-order kinetics at concentrations below 10 mM in the affluent medium. The K-m of the glycerol phosphorylation was 10 muM and the K-i of the L-glycerol 3-phosphate inhibition was 50 muM. The maximum activity (V) was 3.70 mumoles/min per g liver wet wt. These results are similar to in vitro kinetics of the glycerol kinase, except that K-i was found to be somewhat lower in the intact organ. At low glycerol concentrations, a steep concentration gradient exists across the liver cell membrane. The increase in the lactate to pyruvate concentration ratio during glycerol metabolism is related to the actual concentration of L-glycerol 3-phosphate, not to the rate of glycerol uptake.
mesh_terms: D000818:Animals; D001692:Biological Transport; D001706:Biopsy; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D005990:Glycerol / Q000378:metabolism*; D005991:Glycerol Kinase / Q000378:metabolism*; D005994:Glycerophosphates / Q000494:pharmacology; D007700:Kinetics; D007773:Lactates / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008954:Models, Biological; D009243:NAD / Q000378:metabolism*; D010477:Perfusion; D010770:Phosphotransferases / Q000378:metabolism*; D011773:Pyruvates / Q000378:metabolism; D051381:Rats
chemical_list: D005994:Glycerophosphates; D007773:Lactates; D011773:Pyruvates; D009243:NAD; D010770:Phosphotransferases; D005991:Glycerol Kinase; D005990:Glycerol