Objective To investigate the transcriptional regulation of pacemaker channel I, 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 ETB 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.%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1～3 d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的这一作用可被其ETA受体阻断剂BQ-123阻断,而非ETB受体阻断剂BQ-788,而且特异性p38 MAPK抑制剂SB-203580也不影响ET-1的作用.结论 ET-1通过一种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If的表达.这一作用与ET-1致心律失常机制有关.
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