IK channels are involved in the regulatory volume decrease in human epithelial cells |
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Authors: | Wang Jun Morishima Shigeru Okada Yasunobu |
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Institution: | Department of Cell Physiology, National Institute for Physiological Sciences, Myodaiji-cho, Okazaki 444-8585, Japan. |
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Abstract: | Parallel activation ofCa2+-dependent K+ channels and volume-sensitiveCl channels is known to be responsible for KCl effluxduring regulatory volume decrease (RVD) in human epithelial Intestine407 cells. The present study was performed to identify theK+ channel type. RT-PCR demonstrated mRNA expression ofCa2+-activated, intermediate conductance K+(IK), but not small conductance K+ (SK1) or largeconductance K+ (BK) channels in this cell line. Whole cellrecordings showed that ionomycin or hypotonic stress activated inwardlyrectifying K+ currents that were reversibly blocked by IKchannel blockers clotrimazole (CLT) and charybdotoxin] but not by SKand BK channel blockers (apamin and iberiotoxin). Inside-out recordingsrevealed the existence of CLT-sensitive single K+-channelactivity, which exhibited an intermediate unitary conductance (30 pS at 100 mV). The channel was activated by cytosolic Ca2+ ininside-out patches and by a hypotonic challenge in cell-attached patches. The RVD was suppressed by CLT, but not by apamin oriberiotoxin. Thus we conclude that the IK channel is involved in theRVD process in these human epithelial cells. |
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