急性低温/再复温对大鼠心室肌膜电位和钾电流的影响(英文)

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

本文旨在研究急性低温/再复温对大鼠心室肌膜电位和钾电流的影响。膜电位和膜电流分别在全细胞膜片钳的电压钳和电流钳模式下记录。当细胞外灌流液从25oC降低到4oC后,一过性外向电流(transient outward current,Ito)完全消失,膜电位为+60mV时的稳态外向K+电流(sustained outward K+current,Iss)和膜电位为-120mV时的内向整流K+电流(inward rectifier K+current,IK1)分别降低(48.5±14.1)%和(35.7±18.2)%,同时,膜电位绝对值降低。当细胞外灌流液从4oC再升高到36oC后,膜电位出现一过性超级化,然后恢复到静息电位水平;在58个细胞中,有36个细胞伴随复温出现ATP-敏感性K+(ATP-sensitive K+,KATP)通道的激活。再复温引起的上述变化可以被Na+/K+-ATP酶抑制剂哇巴因(100μmol/L)所抑制。再复温引起的KATP通道激活也能被蛋白激酶A抑制剂H-89(100μmol/L)所抑制。在细胞膜电位被钳制在0mV时,当细胞外灌流液温度从25oC降低到4oC后,细胞的体积没有发生明显改变,但当再复温引起KATP通道激活后,细胞很快发生皱缩,同时细胞内部出现许多折光较强的斑点。上述结果表明急性低温/再复温对大鼠心室肌膜电位和K+电流有明显影响,并提示KATP通道激活可能与心肌低温/再复温损伤有关。

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 ＋60 mV and the inward rectifier K^＋ current （IK1） at -120 mV 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 （100 μmol/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 0 mV. However, significant cell 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.