Electrogenicity of hepatocellular fatty acid uptake.
Sensitivity of cellular fatty acids uptake to the membrane potential difference is still a matter of controversy. For direct evaluation of potential sensitivity the effect of changing membrane potential on uptake of a fluorescent long chain fatty acid derivative, 12-NBD-stearate, in isolated rat hepatocytes, was examined. Changes in membrane potential were achieved by patch clamp procedures. Fatty acid influx was simultaneously determined by recording of cell fluorescence. Hyperpolarization from -30 to -70 mV accelerated fatty acid influx whereas depolarization to +50 mV reduced uptake. After obtaining equilibrium hyperpolarization increased cell fluorescence, whereas depolarization pushed NBD-stearate out of cells. Potential sensitivity of uptake was dependent on the fatty acid concentrations in the medium with most prominent effects at low unbound concentrations. These data show that, at low fatty acid concentrations, uptake is, in part, driven by an intracellular negative electric membrane potential.
Elsing
C
C
Gastroenterology, Department of Medicine, University of Heidelberg, Bergheimerstrasse 58, D-69115 Heidelberg, Germany. christoph_elsing@krzmail.krz.uni-heidelberg.de
Kassner
A
A
Gajdzik
L
L
Graf
J
J
Stremmel
W
W
D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D000818:Animals; D001693:Biological Transport, Active; D005227:Fatty Acids / Q000493:pharmacokinetics*; D066298:In Vitro Techniques; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D013228:Stearates / Q000493:pharmacokinetics
D005227:Fatty Acids; D013228:Stearates; C060027:12-N-methyl-7-nitrobenzo-2-oxa-1,3-diazolamino stearate; D009327:4-Chloro-7-nitrobenzofurazan