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目的观察 I_(to)第2个成分 I_(to2)即钙离子激活性氯通道(CLCA)是否参与心力衰竭(心衰)心脏的功能重塑。方法快速起搏犬右心室,诱发心衰,酶学法分离心肌细胞,以经典膜片钳全细胞记录法评价心衰时 I_(to2)电流密度的变化、I_(to2)与 L-型钙通道电流(I_(Ca-L))的关系和在恒定的细胞内钙浓度条件下 I_(to2)与膜电压的关系。用氯通道阻断剂4,4′diisothiocyanostilbene-2,2′-disulfonic acid(DIDS)200μmol 筛选出 I_(to2)。结果 I_(to2)电压-电流关系呈倒钟型,与 I_(Ca-L)的曲线成镜影关系但右移10 mV_oI_(Ca-L)密度在心衰和对照组之间差异无统计学意义。在膜电压0～40 mV 之间,I_(to2)密度在心衰组明显减小。例如膜电压为20 mV 时,对照组与心衰组 I_(to2)分别为(3.02±0.55)pA/pF(n=7)和(1.31±0.25)pA/pF(n=8),P<0.05。I_(to2)电流的衰退时间常数在两组间差异无统计学意义。当细胞内钙浓度锁定在100μmol 时,I_(to2)密度在心衰组反而比对照组增大,提示 CLCA 功能上调。结论心衰时 I_(to2)密度下降,这可能与心衰细胞兴奋释放钙浓度下降有关。I(to2)密度下降可能参与心衰时的动作电位时程延长和晚期后除极的发生,可能是心衰时心律失常的发生机制之一。
Objective To observe whether I_ (to2), the second component of calcium ion-activated chloride channel (CLCA), is involved in the functional remodeling of heart failure in heart failure. Methods Right ventricular myocardium was rapidly paced, heart failure was induced and cardiomyocytes were separated by enzymatic method. The change of I_ (to2) current density was evaluated by classic patch-clamp whole cell recording. I_ (to2) and L- Channel current (I_ (Ca_L)) and the relationship between I_ (to2) and membrane voltage under a constant intracellular calcium concentration. I_ (to2) was screened with 200 μmol of chlorine channel blocker 4,4’diisothiocyanostilbene-2,2’-disulfonic acid (DIDS). Results The voltage-current relationship of I_ (to2) showed an inverted bell-shaped pattern with a mirror image of the I_ (Ca_L) curve but shifted to the right by 10 mV_oI_ (Ca_L). There was no statistical difference between the HF group and the control group significance. In the membrane voltage 0 ~ 40 mV, I_ (to2) density in heart failure group decreased significantly. For example, when the membrane voltage was 20 mV, the control group and the heart failure group had (IO2) (3.02 ± 0.55) pA / pF (n = 7) and 1.31 ± 0.25 pA / pF 0.05. The decay time constant of I_ (to2) current had no significant difference between the two groups. When the intracellular calcium concentration was locked at 100μmol, I_ (to2) density in heart failure group instead of the control group increased, suggesting that CLCA function. Conclusion The density of I_ (to2) decreased in heart failure, which may be related to the decrease of calcium concentration in heart failure cells excited by excitability. Decreased density of I (to2) may be involved in the prolongation of action potentials and the development of post-late depolarization, which may be one of the mechanisms of arrhythmia in heart failure.