大鼠心脏移植物排斥反应时心肌瞬时外向钾电流与心肌细胞动作电位变化的研究

摘要

目的:通过复制大鼠心脏移植模型,研究心肌瞬时钾电流在心脏移植物排斥反应时的变化,及动作电位变化.方法:复制大鼠腹部心脏移植模型,对照组(n=20)为Lewis-Lewis同基因移植,实验组(n=20)为Brown Norway-Lewis异基因移植.于移植后第2～4天处死大鼠,取心脏移植物进行病理检查并利用全细胞膜片钳技术记录心肌细胞动作电位(AP)、心肌瞬时外向钾电流(Ito)及内向整流钾电流(Ik1).结果:大鼠腹部心脏移植模型复制成功,组织学可见对照组心脏移植物在移植后无明显排斥反应,而实验组在移植后第2、4天有轻度到中重度排斥反应;在移植后第2天,两组心肌细胞瞬时外向钾电流(Ito)密度无明显差异;第4天,实验组较对照组Ito密度显著下降,内向整流钾电流(Ik1)显著下降(P＜0.05).在移植后第2、4天,实验组较对照组心肌细胞动作电位时程(APD)均显著延长(P＜0.01).结论:在大鼠心脏移植物排斥反应发生时,心肌细胞APD明显延长,Ito及Ik1密度均显著下降.%Objective:To characterize the variations of transient outward potassium current (Ito) and action potential(AP) in cardiomyocytes during acute cardiac rejection in abdominal heart transplantation model in rats.Methods:Heterotopic heart transplantation was performed in allogeneic (Brown Norway-to-Lewis) and isogeneic(Brown Norway-to-Brown Norway) rats.Recipients were sacrificed at the 2nd day and the 4th day after operation.Histopathological examinations of grafted hearts were performed in half rats of each group randomly.The other half of grafted hearts were excised rapidly and enzymatically dissociated to obtain single cardiomyocytes.Ito,inward rectifier potassium curren(Ik1) and AP were recorded using whole cell patch-clamp technique.Results:Histologic examination showed mild rejection at the 2nd day and moderate rejection at the 4th day in allogeneic group after cardiac transplantation,while no evidence of histologic lesions of rejection in isogeneic group.Under-40-60mV test potential,there is no significant difference between two groups about the current density of Ito,however,it was significantly decreased at the 4th day after cardiac transplantation.Under150--90mV test potential the current density of Ik1 was significantly decreased also.Compared with isogeneic group,action potential duration (APD) of cardiomyocytes in allogeneic group was significantly prolonged (APD90 was (49.28 ± 5.621) mV in isogeneic group,(88.08 ± 6.445) mV in allogeneic group at the 2nd day,P =0.0016;APD90 was (59.34 ± 5.183) mV in isogeneic group,(104.0 ± 9.523) mV in allogeneic group at the 4th day (P =0.0064).Conclusion:APD of cardiomyocytes was significantly prolonged during acute cardiac rejection in rats.Under-40-60mV test potential the current density of Ito was significantly decreased at the 4th day after cardiac transplantation.Under-150 to-90mV test potential the current density of Ik1 was significantly decreased also.