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Effects of acute cooling/rewarming on membrane potential and K~(+) currents in rat ventricular myocytes

Li Longtian, Zhang Libin, Si Yanli, Xiao Fucheng, Li Da, Gao Shan, Li Dongliang, Zhou Shisheng

Liaoning Key Laboratory of Biophysics,Institute of Basic Medical Sciences,Medical College,Dalian University.Dalian 116622,Liaoning；China

Abstract

The effects of acute cooling/rewarming on cardiac K~(+) currents and membrane potential were investigated. Membrane potential and current were assessed with whole-cell patch-clamp technique in current- and voltage-clamp modes. When the temperature of bath solution was decreased from 25℃ to 4℃, the transient outward current (I_(to)) was completely abolished, the sustained outward K~(+) current (I_(ss)) and the inward rectifier K~(+) current (I_(K1)) were depressed by (48.5±14.1)% at +60 mV and (35.7±18.2)% at -120 mV, respectively, and the membrane potential became more positive. After the temperature of bath solution was raised from 4℃ to 36℃, the membrane potential exhibited a transient hyperpolarization and then was maintained at a stable level. In some myocytes (36 out of 58), activation of the ATP-sensitive K~(+) (K_(ATP)) channel after rewarming was observed. The rewarming-induced change in the membrane potential was inhibited by the Na~(+)/K~(+)-ATPase inhibitor ouabain, and the rewarming-elicited activation of K_(ATP) channel was inhibited by the protein kinase A inhibitor H-89. Moreover, decrease of the temperature from 25℃ to 4℃ did not induce any significant change in cell volume when the cell membrane potential was clamped at 0 mV. However, significant cell shrinkage with spots was observed soon after rewarming-induced activation of K_(ATP) channel. These data demonstrate that acute cooling/rewarming have a profound influence on the membrane potential and K~(+) currents of ventricular myocytes, and suggest that activation of K_(ATP) channel may play a role in cardiac cooling/rewarming injury.

Key words: hypothermia;rewarming;Potassium channels;membrane potentials;myocardium

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Citing This Article：

Li Longtian, Zhang Libin, Si Yanli, Xiao Fucheng, Li Da, Gao Shan, Li Dongliang, Zhou Shisheng. Effects of acute cooling/rewarming on membrane potential and K~(+) currents in rat ventricular myocytes. Acta Physiol Sin 2008; 60 (3): 311-319 (in Chinese with English abstract).