Characterization of high-conductance anion channels in rat bile duct epithelial cells

J. M. McGill, S. Basavappa, J. G. Fitz

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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 ~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 P(HCO3/- )/P(Cl-) = 0.51 ± 0.03 (n = 5), P(gluconate)/P(Cl-) = 0.12 ± 0.04 (n = 7), and P(Na+)/P(Cl-) = 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.

Original languageEnglish (US)
Pages (from-to)G703-G710
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume262
Issue number4 25-4
StatePublished - May 27 1992

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Keywords

  • chloride conductance
  • epithelial transport
  • patch clamp

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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