title: Characterization of high-conductance anion channels in rat bile duct epithelial cells.
abstract: We have utilized patch clamp recording techniques to identify a high-conductance anion channel in the plasma membrane of rat bile duct epithelial cells. Cells were isolated from the intrahepatic bile duct 2-6 wk after bile duct ligation. Channels were present in 27% (28/102) of excised patches, and, with 150 mM Cl- in bath and pipette solutions, the slope conductance of the fully open level was approximately 364 +/- 18 pS (n = 8) with current reversal = 0 +/- 1 mV. Channel characteristics were not affected by substitution of K+ for Na+ in the pipette solution; but substitution of HCO3-, gluconate, or increased NaCl caused a shift in the reversal potential toward the new equilibrium potential for Cl-. The permeability ratios were PHCO3-/PCl- = 0.51 +/- 0.03 (n = 5), Pgluconate/PCl- = 0.12 +/- 0.04 (n = 7), and PNa+/PCl- = 0.11 +/- 0.02 (n = 3). Current transitions to a subconductance level at 72% of the fully open level were present in most studies. Channel open probability was greatest near 0 mV and decreased rapidly outside of -20 to +20 mV because of voltage-dependent channel closure. The time course for current relaxation of summed single channel currents could be described by a single exponential with more rapid channel closure as the magnitude of the voltage step away from 0 mV increased. In the cell-attached configuration, the channel was rarely open (4/35, 11%) but opening could be induced by negative pipette pressure (5/14, 35%). Possible physiological roles for this channel are discussed.
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: J M
authors.initials: JM
authors.lastname: McGill
authors.forename: S
authors.initials: S
authors.lastname: Basavappa
authors.forename: J G
authors.initials: JG
authors.lastname: Fitz
mesh_terms: D000818:Animals; D000838:Anions / Q000378:metabolism*; D001639:Bicarbonates / Q000378:metabolism; D001652:Bile Ducts / Q000166:cytology / Q000502:physiology*; D002712:Chlorides / Q000494:pharmacology; D004553:Electric Conductivity; D004594:Electrophysiology; D004847:Epithelial Cells; D004848:Epithelium / Q000502:physiology; D005942:Gluconates / Q000494:pharmacology; D007473:Ion Channels / Q000378:metabolism / Q000502:physiology*; D010539:Permeability; D051381:Rats
chemical_list: D000838:Anions; D001639:Bicarbonates; D002712:Chlorides; D005942:Gluconates; D007473:Ion Channels; C030691:gluconic acid