Whole cell patch clamping of ciliary epithelial cells during anisosmotic swelling.
Anisosmotic cell swelling triggers a regulatory volume decrease (RVD) in cell lines derived from human nonpigmented ciliary epithelium. Measurements of cell volume have indicated that the RVD reflects activation of K+ and/or Cl- channels. We have begun to characterize the putative channels by whole cell patch clamping. The results obtained by altering the external K+ and Cl- concentrations and by adding 20-50 microM quinidine or 1 mM Ba2+ indicate that K+ conductances contribute substantially and Cl- conductances contribute very little to the total membrane conductance (GT) under baseline isotonic conditions. Reducing the external osmolality by 20-50% reversibly and reproducibly increased GT by an order of magnitude. Data obtained from ion substitutions and the channel blockers quinidine and 5-nitro-2-(3-phenylpropylamino)-benzoate indicate that most of the hypotonicity-induced conductance reflects stationary Cl(-)-channel activity. The contribution of new K(+)-channel activity was small at intracellular free Ca2+ concentrations of 10 or 200 nM. We conclude that the RVD triggered by bath hypotonicity primarily reflects increased Cl(-)-channel activity.
Yantorno
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Department of Physiology, University of Pennsylvania, Philadelphia 19104.
Carré
D A
DA
Coca-Prados
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M
Krupin
T
T
Civan
M M
MM
D002712:Chlorides / Q000378:metabolism / Q000502:physiology; D002924:Ciliary Body / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D004594:Electrophysiology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism / Q000502:physiology; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D009995:Osmosis; D011188:Potassium / Q000378:metabolism / Q000502:physiology
D002712:Chlorides; D007038:Hypotonic Solutions; D011188:Potassium