Long-chain fatty acid uptake by skeletal myocytes: a confocal laser scanning microscopy study.
Studies of regulation of free fatty acid (FFA) utilization by skeletal muscles have focused on plasma FFA delivery and on intracellular factors affecting FFA metabolism. The present study was conducted to directly analyse the uptake process of fatty acids into single myocytes. Cells were isolated from the rat flexor digitorum brevis muscle. Confocal laser scanning microscopy was utilized to analyse the uptake of the fluorescent fatty acid derivative 12-NBD-stearate, which is not metabolized by muscle tissue. Uptake represented a saturable function of the unbound fatty acid concentration in the medium (K(m) 366 +/- 118 nM, Vmax 2.1 +/- 0.3 AU/s) and depended on the medium sodium concentration. Reduced buffer pH increased initial uptake rates, whereas lactate (10 mM) had no effect. Membrane hyper- and depolarization decreased uptake rates. This study demonstrates for the first time kinetic data from isolated myocytes with evidence for a carrier-mediated transport mechanism for long-chain fatty acids.
Elsing
C
C
Department of Medicine, University of Heidelberg, Germany. christoph_elsing@krzmail.krz.uni-heidelberg.de
Górski
J
J
Boeker
C
C
Stremmel
W
W
D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000493:pharmacokinetics*; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D019344:Lactic Acid / Q000494:pharmacology; D008055:Lipids / Q000032:analysis; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D018613:Microscopy, Confocal; D018482:Muscle, Skeletal / Q000502:physiology*; D018996:Myelin P2 Protein / Q000378:metabolism; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D051381:Rats; D017208:Rats, Wistar; D013228:Stearates / Q000493:pharmacokinetics; D014634:Valinomycin / Q000494:pharmacology
D002352:Carrier Proteins; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D007476:Ionophores; D008055:Lipids; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D013228:Stearates; C060027:12-N-methyl-7-nitrobenzo-2-oxa-1,3-diazolamino stearate; D014634:Valinomycin; D019344:Lactic Acid; D009327:4-Chloro-7-nitrobenzofurazan