Ca2+-and voltage activated K+ channel in apical cell membrane of gallbladder epithelium fromTriturus |
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Authors: | Y Maruyama H Matsunaga T Hoshi |
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Institution: | (1) Department of Physiology, Faculty of Medicine, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113 Tokyo, Japan |
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Abstract: | The presence of Ca2+- and voltage-activated K+ channels was directly demonstrated in the apical cell membrane of gallbladder epithelium by patch-clamp single-channel current recording. In K+-depolarized epithelial cells, negative pipette potentials induced outward current steps when the patch-pipette was filled with Na+-rich solution and these current steps were not affected by the presence or absence of Cl–. When K+-rich solution was in the pipette and K+-depolarized cells were examined, the current-voltage relations were linear with a single-channel conductance of 140 pS and polarity was reversed at 0 mV. In excised inside-out membrane patches, raising the free Ca2+ concentration of the medium facing the inner side of the membrane from 10–7 to 10–6 M evoked a marked increase in open state probability of the channels without affecting the elementary current steps. This suggests that intracellular Ca2+ as a second messenger plays a crucial role in the regulatory mechanism of the membrane potential by modulating the high-conductance apical K+ channels. |
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Keywords: | Apical cell membrane K+ channel Patch-clamp Gallbaladder Ca2+ activation Voltage activation |
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