Internal and external K+ help gate the inward rectifier.

I S Cohen; D DiFrancesco; N K Mulrine; P Pennefather

doi:10.1016/s0006-3495(89)82792-4

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Internal and external K+ help gate the inward rectifier.

I S Cohen·D DiFrancesco·N K Mulrine·P Pennefather

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Abstract

Recent investigations have demonstrated substantial reductions in internal [K+] in cardiac Purkinje fibers during myocardial ischemia (Dresdner, K.P., R.P. Kline, and A.L. Wit. 1987, Circ. Res. 60: 122-132). We investigated the possible role these changes in internal K+ might play in abnormal electrical activity by studying the effects of both internal and external [K+] on the gating of the inward rectifier iK1 in isolated Purkinje myocytes with the whole-cell patch-clamp technique. Increasing external [K+] had similar effects on the inward rectifier in the Purkinje myocyte as it does in other preparations: increasing peak conductance and shifting the activation curve in parallel with the potassium reversal potential. A reduction in pipette [K+] from 145 to 25 mM, however, had several dramatic previously unreported effects. It decreased the rate of activation of iK1 at a given voltage by several-fold, reversed the voltage dependence of recovery from deactivation, so that the deactivation rate decreased with depolarization, and caused a positive shift in the midpoint of the activation curve of iK1 that was severalfold smaller than the associated shift of reversal potential. These changes suggest an important role of internal K+ in gating iK1 and may contribute to changes in the electrical properties of the myocardium that occur during ischemia.

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Animals Dogs Heart Conduction System In Vitro Techniques Kinetics Membrane Potentials Potassium Potassium Channels Purkinje Fibers Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S.

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I S Cohen, D DiFrancesco, N K Mulrine, P Pennefather. 1989. Internal and external K+ help gate the inward rectifier.. https://doi.org/10.1016/s0006-3495(89)82792-4

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