Activation propetties of the inward-recifying potassium channel on mammalian heart cells |
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Authors: | Yves Tourneur Raman Mitra Martin Morad Oger Rougier |
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Institution: | (1) Laboratoire de Physiologie des Elements Excitables, C.N.R.S.U.A. 244 Université Claude Bernard, F 69622 Villeurbanne Cedex, France;(2) Department of Physiology, School of Medicine, University of Pennsylvania, 19104 Philadelphia, Pennsylvania |
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Abstract: | Summary The early phase of activation of the inward-rectifying potassium channel is studied on single cells from guinea-pig heart. The current is quasi-instantaneous when it is outward, but activates with time when it is inward. This relaxation is exponential and its time-constant decreases with hyperpolarization. TheI/V curve reflects a strong inward rectification and has a negative slope conductance on depolarization. Similar results were recorded in the absence of sodium, calcium, chloride ions and in isotonic potassium. Cesium slows down the phase of activation, and eventually appears to block the channels by suppression of the activation. Barium, conversely, does not affect the activation, but promotes an inactivation of this current, which blocks it. These results are independent on the cells' dissociation method. They suggest that this current is the inward rectifier, calledI
K1 on heart. Its activation curve suggests that the inward and outward currents are flowing through the same channels. The inward rectifier is time-and voltage-dependent on heart as on other tissues. The effects of cesium and barium are also similar. The importance of its negative slope conductance is discussed. |
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Keywords: | heart ventricular cells patch clamp whole cell recording inward rectification potassium channels |
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