模拟缺血对左心室心肌细胞瞬间外向钾电流跨壁异质性的影响

Effects of Simulated Ischemia on the Transient Outward Potassium Current Heterogeneity of Myocytes from Rabbit Left Ventricular Free Wall

目的研究模拟缺血对左心室心肌细胞瞬间外向钾通道电流(Ito)的跨壁异质的影响。方法采用膜片钳全细胞模式记录左心室3层心肌细胞的Ito,并观察模拟缺血对心肌Ito跨壁异质性的影响。结果左心室3层细胞的Ito电流存在异质性,表现为心外膜层(Epi)的Ito电流密度-电压关系(I-V)曲线最高,测试电压+70mV的Ito电流密度Epi明显大于中层细胞(M)和心内膜细胞(Endo),Epi、Endo和M的Ito电流密度分别为113.06±16.32(n=10),30.12±6.58(n=9)和51.43±5.68 pA/pF(n=8)。3层细胞的Ito失活无明显差异,M细胞的Ito失活后再恢复最慢。模拟缺血后,Epi的Ito I-V曲线呈时间依赖性下移,Endo呈时间依赖性上移,M细胞先上移然后下移;M细胞的Ito失活曲线左移,而Epi和Endo右移;模拟缺血3层细胞的Ito失活后再恢复无明显差异。结论左心室心肌细胞的Ito存在跨壁异质性;模拟缺血缺氧增加了兔左心室Ito的跨壁异质性。

Objective To study the transmural heterogeneity of transient outward potassium current （Ito） of myecytes from left ventricular free wall in rabbit and the influence of simulated ischemia, Methods Single ventricular myocytes were enzymatically isolated from rabbit left free wall, Ito was recorded using patch clamp techniques in the whole cell configuration. Then simulated ischemia was given to the myocytes and ho was recorded again, Results The Ito density in epicardial cells（Epi） was bigger than that in midmyocardial （M） and endocardial cells （Endo） during ＋ 70mV, the Ito density of Epi, Endo and M were respectively（ 113.06 ± 16,32） pA/pF （ n = 10 cells）. （30.12 ± 6.58） pMpF （ n = 9 cells） and （51.43 ± 5.,68）pA/pF （ n = 8 cells）. There were no significant differences in the lto inactivation curves among the three subtypical ceils, The Ito recovery curve from inactivation recovered more slowly in M cells than that in Epi and Endo ceils, After simulated ischemia, the Ito I - V curve decreasd in Epi, increased in Endo and M. The Ito inactivation curve of M cells shifted in the hyperpolarization direction, while the Ito inactivation curves of Epi and Endo shifted in the depolarization direction. There were no significant differences in the Ito recovery curves from inactivation among the three subtypical cells. Conclusion There is transmural heterogenneity of Ito in the rabbit left ventricular free wall; the Ito heterogeneity is signif- icantly increased by simulated ischemia.