Oscillating activity of a calcium-activated K+ channel in normal and cancerous mammary cells in culture |
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Authors: | Koh-Ichi Enomoto Kishio Furuya Takashi Maeno Charles Edwards Takami Oka |
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Affiliation: | (1) Department of Physiology, Shimane Medical University, 693 Izumo Shimane, Japan;(2) Department of Cellular Physiology, National Institute for Physiological Sciences, 444 Okazaki, Japan;(3) College of Medicine, University of South Florida, 33612 Tampa, Florida;(4) Laboratory of Molecular and Cell Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, 20892 Bethesda, Maryland |
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Abstract: | Summary Calcium-activated potassium channels were the channels most frequently observed in primary cultured normal mammary cell and in the established mammary tumor cell, MMT060562. In both cells, single-channel and whole-cell clamp recordings sometimes showed slow oscillations of the Ca2+-gated K+ current. The characteristics of the Ca2+-activated K+ channels in normal and cancerous mammary cells were quite similar. The slope conductances changed from 8 to 70 pS depending on the mode of recording and the ionic composition in the patch electrode. The open probability of this channel increased between 0.1 to 1 m of the intracellular Ca2+, but it was independent of the membrane potential.Charybdotoxin reduced the activity of the Ca2+-activated K+ channel and the oscillation of the membrane current, but apamin had no apparent effect. The application of tetraethylammonium (TEA) from outside and BaCl2 from inside of the cell diminished the activity of the channel. The properties of this channel were different from those of both the large conductance (BK or MAXI K) and small conductance (SK) type Ca2+-activated K+ channels. |
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Keywords: | Ca2+-activated K+ channel Ca2+ oscillation inward rectification charybdotoxin apamin |
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