内皮素-1通过一种不依赖于p38 MAPK的信号转导机制刺激心肌细胞起搏通道I_f的表达

Endothelin-1 stimulates the expression of pacemaker channel I_f in cardiomyocytes through a p38 MAPK-independent signaling pathway

目的探讨血管活性肽内皮素-1（ET-1）对新生鼠心室肌细胞起搏通道If表达的影响及其细胞内信号机制。方法采用酶消化法急性分离1～3d龄新生大鼠心室肌细胞，用全细胞膜片钳技术记录If电流，定量RT-PCR技术检测介导If电流的、超极化激活的环核苷酸门控通道亚型HCN2和HCN4的表达。结果ET-1呈剂量和时间依赖性增强了HCN2和HCN4通道亚型的表达，ET-1的这-作用可被其ETA受体阻断剂BQ-123阻断，而非ETR受体阻断剂BQ-788，而且特异性p38MAPK抑制剂SB．203580也不影响ET-1的作用。结论ET-1通过-种ETA受体介导的、不依赖于p38MAPK的信号转导机制刺激了心肌细胞起搏通道，f的表达。这-作用与ET-1致心律失常机制有关。

Objective To investigate the transcriptional regulation of pacemaker channel If mediated by vasoactive peptide endothelin-1 （ET-1） in neonatal rat ventricular myocytes and its mechanism. Methods Neonatal rat ventricular myocytes were enzymatically isolated. If current was recorded using the whole-cell patch-clamp technique. The expression of hyperpolarization-activated cyclic nucleotide-gated channel （HCN） isoforms HCN2 and HCN4 were measured by quantitative RT-PCR. Results ET-1 increased the expression of HCN2 and HCN4 mRNA in a dose- and time-dependent manner. These effects were blocked by specific ETA receptor antagonist BQ-123 but not the ETa receptor antagonist BQ-788. The effects of ET-1 on HCN2 and HCN4 mRNA expression were not affected by the p38 mitogen-activated protein kinase （MAPK） inhibitor （SB-203580）. Conclusion These findings indicate that ET-1 stimulates the expression of pacemaker channel If in cardiomyocytes via ETA receptor through a p38 MAPK-independent signaling pathway, which might be linked to the intrinsic arrhythmogenic potential of ET-1.