Objective: To observe the effects of hypothermia on the repolarization duration and the expression of Kir2.1 protein of ventricular myocytes in isolated rat heart and explore the role of Kir2.1 protein.Methods: Eighteen healthy adult male Sprague-Dawley rats were randomly divided into three groups (n=6 per group): Control group (C group), 35℃ group (H1 group), 32℃ group (H2 group). Langendorff isolated heart models were established. After 15 min 37℃ K-H fluid banlanced perfusion, C group continued to perfuse the K-H solution at 37℃ for 30 minutes, H1 group continued to perfuse the K-H solution at 35℃ for 30 minutes, H2 group continued to perfuse the K-H solution at 32℃ for 30 minutes. At 15 min of balanced perfusion (T1), and 30 min of continuous perfusion (T2), the heart rate,and the MAP in the three layers of the left ventricular anterior wall were recorded, the action potential duration at 50% repolarization (MAPD50), the action potential duration at 90% repolarization (MAPD90) and transmural dispersion of repolarization(TDR) were calculated. At the same time, the occurrence of arrhythmia was recorded. The expression of Kir2.1 protein was measured by Western blot. The average optical density (AOD) and the distribution of Kir2.1 protein were measured by immunohistochemistry in the ventricular tissue measured by electrophysiology. Results: Compared with T0, the heart rate was decreased, MAPD50 and MAPD90 were prolonged significantly (P＜0.05), and TDR was increased significantly (P＜0.05) in H1 group, H2 group at T1. Compared with C group, the HR was decreased, the MAPD90 was prolonged significantly (P＜0.05), TDR was increased significantly (P＜0.05),the expression and the AOD of Kir2.1 protein were decreased significantly (P＜0.05) in H1group, H2group at T1. Compared with H1 group, the heart rate of H2 group was decreased significantly (P＜0.05), MAPD50 and MAPD90 were prolonged significantly (P＜0.05), and TDR was increased significantly (P＜0.05) at T1. The distribution of Kir2.1 protein in group C was normal, while the distribution of Kir2.1 in H1 group and H2 group was disordered. Conclusion: Hypothermia prolonged the ventricular duration of repolarization and increased the dispersion of repolarization. The mechanism is related to the down-regulation the expression of Kir2.1 protein and the disorder of the distribution of Kir2.1 protein.
目的: 观察低温对离体大鼠心室肌复极时程及Kir2.1蛋白表达的影响,探讨Kir2.1蛋白在其中的作用。 方法:18只健康雄性SD大鼠, 随机分为3组(n=6),即正常对照组(C组)、35℃低温组(H1组)和32℃低温组(H2组)。制备Langendorff离体心脏灌注模型,37℃ K-H液平衡灌注15 min后,C组继续灌注37℃ K-H液30 min;H1组继续灌注35℃的K-H液30 min,H2组继续灌注32℃的K-H液30 min。记录各组平衡灌注15 min(T1)和继续灌注30 min(T2)时HR、左心室前壁三层心肌单相动作电位,计算单相动作电位复极50％、90％的时程(MAPD50、MAPD90)和跨室壁复极离散度(TDR),同时记录心律失常发生情况。取测量电生理的心室肌部位组织以Western blot测定Kir2. 1蛋白表达,以免疫组织化学法测量Kir2. 1蛋白的平均光密度值(AOD)及分布情况。结果: 与T0比较,T1时H1组和H2组HR显著减慢(P＜0.05), MAPD50、MAPD90显著延长(P＜0.05),TDR显著增大(P＜ 0.05);与C组比较,T1时H1组和H2组HR显著减慢(P＜0.05),MAPD90显著延长(P＜0.05),TDR显著增大(P＜ 0.05),Kir2.1蛋白表达显著减少(P＜0.05), AOD值显著减少(P＜0.05)。与H1组比较,T1时H2组心率显著减慢(P＜0.05),MAPD50、MAPD90显著延长(P＜0.05),TDR显著增大(P＜0.05)。C组Kir2.1蛋白分布正常,H1、H2组蛋白分布紊乱。结论: 低温会延长心室复极时程,增加复极离散度,其机制与低温下调Kir2.1蛋白表达、改变Kir2.1蛋白分布有关。.
Keywords: Kir2.1; arrhythmia; electrophysiological techniques; hypothermia; monophasic action potential; transmural dispersion of repolarization.