Selective modulation of the ATP-sensitive K+ channel by nicorandil in guinea-pig cardiac cell membrane |
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Authors: | M. Takano A. Noma |
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Affiliation: | (1) Department of Physiology, Faculty of Medicine, Kyushu University, 812 Fukuoka, Japan |
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Abstract: | Summary Effects of a vasodilator, nicorandil (2-nicotinamidoethyl nitrate) on four kinds for cardiac K+ channels were investigated in guinea pig ventricular and atrial cells using inside-out patch recording combined with oilgate concentration jump method.Nicorandil of 300 mol/l failed to affect the inward-rectifier K+ channel and the Na+-activated K+ channel. The open probability of the muscarinic K+ channel, when activated by the application of GTP, was not changed by the drug. Nicorandil selectively increased the open probability of the ATP-sensitive K+ channel that was partly suppressed by intracellular ATP. The median effective concentration (EC50) of nicorandil was 74 mol/l and Hill coefficient was 1.32 in the concentration-open probability relationship. The closing rate of the K+ channel by ATP was markedly delayed by the drug, whereas the open rate on removal of ATP was scarcely affected. Nicorandil had only little effect on this channel after run-down. It was concluded that nicorandil selectively activates the ATP-sensitive K+ channel mainly by modulating the ATP-dependent gate.Send offprint requests to M. Takano at the above address |
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Keywords: | Nicorandil (2-nicotinamidoethyl nitrate) Cardiac myocyte ATP-sensitive K+ channel |
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