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

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Author:
No author available
Journal Title:
ACTA PHYSIOLOGICA SINICA
Issue:
3
DOI:
10.3321/j.issn:0371-0874.2008.03.001
Key Word:
低温;再复温;钾通道;膜电位;心肌;hypothermia;rewarming;potassium channels;membrane potentials;myocardium

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 (Ito) was completely abolished, the sustained outward K+ current (Iss) at +60mV and the inward rectifier K+ current (IK1) at-120mV were depressed by (48.5±14.1)% and (35.7±18.2)%, 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+ (KATP) channels after rewarming was observed. The rewarming-induced change in the membrane potential was inhibited by the Na+/K+-ATPase inhibitor ouabain (100μmol/L), and the rewarming-elicited activation of KATP channels was inhibited by the protein kinase A inhibitor H-89 (100μmol/L). 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 O mV. However, significant ceil shrinkage with spots was observed soon after rewarming-induced activation of KATP channels. These data demonstrate that acute cooling/rewarming has a profound influence on the membrane potential and K+ currents of ventricular myocytes, and suggest that activation of KATP channels may play a role in cardiac cooling/rewarming injury.

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