Renal palmitate transport: possible sites for interaction with a plasma membrane fatty acid-binding protein.
In previous studies from this laboratory, a mediated transport system for long chain fatty acids was observed in rat renal basolateral membrane vesicles. Transport was measured in the absence of albumin and indicated the presence of a Na+ independent anion exchange mechanism. The present experiments were done to characterize renal transport of fatty acids derived from fatty acid-albumin complexes. 3H-palmitate uptake by brush border (BBMV) and basolateral membrane vesicles (BLMV) isolated from rat renal cortex was determined using a rapid filtration technique. All incubation media contained 100 microM 3H-palmitate complexed to 100 microM bovine serum albumin. Up to 65% of initially bound fatty acid-albumin complexes were displaceable by washing with solution containing 0.1% albumin. Total palmitate uptake was measured as the remaining non-displaceable radioactivity. In BBMV in low ionic strength (300 mM mannitol) or ionic buffers (100 mM mannitol + 100 mM NaCl or KCl), total palmitate uptake at 15 sec did not differ from equilibrium (60 min) values of 10-11 nmoles/mg protein. Uptake was primarily due to binding. A similar pattern was seen with BLMV in 300 mM mannitol buffer. In BLMV in 100 mM NaCl or KCl buffers, equilibrium uptake was 10-fold lower than at 15 sec. This suggests binding followed by cation-dependent translocation. If a putative FABPPM is involved in transport only, its presence should be confined to BLMV.
Trimble
M E
ME
Department of Physiology, SUNY Health Science Center, Syracuse 13210.
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D007668:Kidney / Q000378:metabolism*; D008353:Mannitol / Q000494:pharmacology; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010168:Palmitates / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012709:Serum Albumin / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D014316:Tritium
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; D010168:Palmitates; D012709:Serum Albumin; D014316:Tritium; D008353:Mannitol; D012964:Sodium; D011188:Potassium