title: Hepatocellular uptake of oleate is energy dependent, sodium linked, and inhibited by an antibody to a hepatocyte plasma membrane fatty acid binding protein.
abstract: Several studies suggest that a portion of hepatocellular nonesterified fatty acid uptake may be carrier mediated. To further investigate this process, initial rates (Vo) of [14C]oleate uptake into rat hepatocytes, isolated by collagenase perfusion and incubated at 37 degrees C with oleate in the presence of bovine serum albumin, were studied as a function of the concentration of unbound [14C]oleate in the medium. Vo was saturable with increasing unbound oleate concentration (Km = 8.3 X 10(-8) M; Vmax = 197 pmol per min per 5 X 10(4) hepatocytes) and was not inhibited by up to 40 microM sulfobromophthalein, taurocholate, or cholic acid. Oleate uptake was sodium dependent. Vo was significantly diminished when Li+, K+, choline, or sucrose were substituted for Na+ in the incubation medium and was reduced 46% by 1 mM ouabain. Uptake was also markedly reduced after exposure of cells to metabolic inhibitors (e.g., 2,4-dinitrophenol, carbonyl cyanide m-chlorophenylhydrazone, antimycin, KCN). To evaluate the physiologic significance of the previously isolated rat liver plasma membrane fatty acid-binding protein, the effect of an antibody directed against this protein on hepatocellular [14C]oleate uptake was examined. Preincubation of hepatocytes with the IgG fraction of this antiserum inhibited Vo of [14C]oleate by up to 65% in dose-related fashion, without altering Vo for [35S]sulfobromophthalein, [14C]taurocholate, or [3H]cholate. These data indicate that at least a portion of hepatocellular oleate uptake is energy dependent, sodium linked, and mediated by a specific liver plasma membrane-fatty acid-binding protein.
authors.forename: W
authors.initials: W
authors.lastname: Stremmel
authors.forename: G
authors.initials: G
authors.lastname: Strohmeyer
authors.forename: P D
authors.initials: PD
authors.lastname: Berk
mesh_terms: D000818:Animals; D000838:Anions / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D010693:Phloretin / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism
chemical_list: D000838:Anions; D002352:Carrier Proteins; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009829:Oleic Acids; D019301:Oleic Acid; D010042:Ouabain; D012964:Sodium; D010693:Phloretin