A large conductance, Ca2+-activated K+ channel in a human lung epithelial cell line (A549).
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.
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Department of Physiology, Dalhousie University, Halifax, Nova Scotia, Canada.
Duszyk
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French
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D000255:Adenosine Triphosphate / Q000378:metabolism; D002460:Cell Line; D004848:Epithelium / Q000737:chemistry; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008168:Lung / Q000737:chemistry*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000032:analysis*; D024681:Potassium Channels, Calcium-Activated; D013757:Tetraethylammonium Compounds / Q000378:metabolism
D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D013757:Tetraethylammonium Compounds; D000255:Adenosine Triphosphate