Anion channels in rat liver canalicular plasma membranes reconstituted into planar lipid bilayers.
Previous studies from this laboratory have demonstrated a Cl(-)-HCO3- exchanger and have provided evidence for a Cl- conductance in rat liver canalicular plasma membrane vesicles. To further investigate the apical Cl- conductance, we performed single-channel analysis after incorporation of canalicular liver plasma membrane vesicles into planar lipid bilayers. This was necessary, because the canalicular membrane is not accessible for the patch-clamp technique. Two types of anion channels could be identified (30- and 90-pS conductance) corresponding to the class of small and intermediate channels, respectively. The kinetics of the small channel were found to be voltage dependent with a maximum for the open probability at -20 mV. In contrast, intermediate channel kinetics were voltage independent. The anion channels described above could allow electrogenic Cl- efflux, to compensate Cl- influx via the electroneutral Cl(-)-HCO3- exchanger. Further studies will be required to prove their functional importance in bile formation.
Sellinger
M
M
Department of Medicine, Yale University School of Medicine, New Haven, Connecticut 06510.
Weinman
S A
SA
Henderson
R M
RM
Zweifach
A
A
Boyer
J L
JL
Graf
J
J
D000818:Animals; D002458:Cell Fractionation; D002462:Cell Membrane / Q000502:physiology; D018118:Chloride Channels; D007473:Ion Channels / Q000502:physiology*; D008051:Lipid Bilayers; D008099:Liver / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000502:physiology*; D008954:Models, Biological; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D011336:Probability; D051381:Rats; D011919:Rats, Inbred Strains
D018118:Chloride Channels; D007473:Ion Channels; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; C021016:1,2-diphytanoylphosphatidylcholine