Hepatocellular influx of [14C]oleate reflects membrane transport rather than intracellular metabolism or binding.
When [14C]oleate bound to bovine serum albumin was incubated at 37 degrees C for 7 min with isolated rat hepatocytes in the absence of glucose, the cumulative oleate uptake curve had two components: a rapid, linear segment over the first 30 sec, followed by a slower, curvilinear component. At 173 microM [14C]oleate/albumin (1:1, mol/mol), the initial component had a slope (Vo) of 118 +/- 18 pmol per min per 5 X 10(4) hepatocytes (mean +/- SD). During this initial 30 sec, virtually no oleate was oxidized, and less than 11% was esterified. By 5 min, 79% was esterified; oxidation never exceeded 4%. Addition of 2 mM glucose significantly increased oleate esterification and thereby available oleate binding sites on cytosolic fatty acid binding protein but had no influence on Vo. Pretreatment with trypsin reduced Vo by 49 +/- 15%. These data indicate that the initial component of the oleate uptake curve reflects predominantly influx, whereas the subsequent component reflects a balance between influx, efflux, and intracellular metabolism. Influx is independent of intracellular binding, oxidation, and esterification and may reflect a membrane-associated carrier-mediated process.
Stremmel
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Berk
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D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism*; D051381:Rats; D012710:Serum Albumin, Bovine / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
D008565:Membrane Proteins; D009829:Oleic Acids; D012710:Serum Albumin, Bovine; D019301:Oleic Acid; D014357:Trypsin