氯沙坦对自发性高血压大鼠心肌细胞钙电流影响的分子机制

Molecular Basis for Losartan Affecting Calcium Current in Spontaneous Hypertensive Rats

目的:探讨自发性高血压大鼠(SHR)心肌细胞L型钙电流(ICa-L)和L型钙通道α1C亚基(CaL-α1C)信使核糖核酸(mRNA)及蛋白的变化,并观察氯沙坦对这些变化的影响以期评估氯沙坦的抗心律失常作用及其分子机制。方法:将SHR按随机数字表法分成以下三组(每组n=10):氯沙坦组、依那普利组和安慰剂组,另选同龄Wistar大鼠作为空白对照(对照组,n=10)。8周后采用膜片钳技术记录左心室心肌ICa-L,并采用逆转录—聚合酶链反应及蛋白质印迹方法测定CaL-α1C的mRNA及蛋白水平。结果:氯沙坦组左心室细胞的50%动作电位持续时间、90%动作电位持续时间比安慰剂组、依那普利组缩短(P均<0.01)。氯沙坦组的ICa-L峰值及电流密度比安慰剂组及依那普利组降低(P均<0.05)。氯沙坦组ICa-L的τ值比安慰剂组及依那普利组升高(P均<0.01)。氯沙坦组的CaL-α1C mRNA及蛋白表达水平比安慰剂组及依那普利组降低(P均<0.05)。上述比较差异均有统计学意义。结论:氯沙坦能缩短单个心肌细胞动作电位时程,延迟L型钙通道失活再激活的恢复时间,通过下调CaL-α1CmRNA及其蛋白水平而发挥作用。

Objective：To investigate the molecular basis for losartan affecting L-type calcium current and the changes of mRNA and protein expression of L-type Ca2＋ channel α1C （CaL-cd C ）subunit in spontaneous hypertensive rats（SHR）. Methods ：SHR were assigned into three groups as Losartan group, Enalapril group and Placebo group, n = 10 in each group. In addition, 10 Wistar rats were used as Control group. All animals were treated for 8 weeks, and then the membrane currents of L- type calcium channels on ventricular myocytes were recorded;RT-PCR and Western blot analysis were performed to examine the mRNA and protein expression of CaL-α1C subunit. Results ：The 50% of action potential duration and 90% of action potential duration in Losartan group were shorter than those in Placebo group and Enalapril group, P〈0. 01 respectively. The current density was decreased in Losartan group than those in Placebo group and Enalapril group ,P〈0. 05 respectively. The recovery time（t） of reactivation of L-type Ca2＋channel in Losartan group was increased than those in Placebo group and Enalapril group,P〈0.01 respectively. The mRNA and protein expression of CaL-α1C subunit in Losartan group was decrease than those in Placebo group and Enalapril group ,P〈0. 05 respectively. Conclusion：Losartan may shorten the action potential duration and delay the recovery time of reactivation of L-type Ca2＋ channel in myocytes by down-regulating the mRNA and protein expression of CaL-α1C subunit in SHR.