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A large conductance, Ca2+-activated K+ channel in a human lung epithelial cell line (A549)

Biochim Biophys Acta. 1997 Jul 25;1327(2):249-58. doi: 10.1016/s0005-2736(97)00073-4.

Abstract

A large conductance, Ca2+-activated K+ channel in a human lung epithelial cell line (A549) was identified using the single channel patch clamp technique. Channel conductance was 242 +/- 33 pS (n = 67) in symmetrical KCl (140 mM). The channel was activated by membrane depolarization and increased cytosolic Ca2+. High selectivity was observed for K+ over Rb+(0.49) > Cs+(0.14) > Na+(0.09). Open probability was significantly decreased by Ba2+ (5 mM) and quinidine (5 mM) to either surface, but TEA (5 mM) was only effective when added to the external surface. All effects were reversible. Increasing cytosolic Ca2+ concentration from 10(-7) to 10(-6) M caused an increase in open probability from near zero to fully activated. ATP decreased open probability at approximately 2 mM, but the effect was variable. The channel was almost always observed together with a smaller conductance channel, although they could both be seen individually. We conclude that A549 cells contain large conductance Ca2+-activated K+ channels which could explain a major fraction of the K+ conductance in human alveolar epithelial membranes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Cell Line
  • Epithelium / chemistry
  • Humans
  • Large-Conductance Calcium-Activated Potassium Channels
  • Lung / chemistry*
  • Patch-Clamp Techniques
  • Potassium Channels / analysis*
  • Potassium Channels, Calcium-Activated*
  • Tetraethylammonium Compounds / metabolism

Substances

  • Large-Conductance Calcium-Activated Potassium Channels
  • Potassium Channels
  • Potassium Channels, Calcium-Activated
  • Tetraethylammonium Compounds
  • Adenosine Triphosphate