小电导钙激活钾通道在人心房肌细胞中的表达及功能

摘要

目的 探讨小电导钙激活钾通道在人心房肌细胞巾的表达情况和功能意义.方法 收集行心内直视手术的窦性心律先心病患者8例,取右心耳组织,行免疫组化分析3种SK通道亚型(SK1、SK2和SK3)表达情况;使用经典两步酶解法分离心房肌细胞,应用穿孔膜片钳和传统电压钳技术分别记录心房肌细胞动作电位(APs)和全细胞的钙激活钾电流(IK,Ca),比较给予SK通道特异性阻断剂apamm(100 nmol/L)前、后动作电位时程(APD)变化.结果 SK1、SK2和SK3通道亚型在心房肌细胞中均呈阳性表达,膜片钳记录证实IK,Ca的存在,且apamin明显延长复极化90%的动作电位时程(APD90),而对APD50无明显影响.结论 3种SK通道亚型在人心房肌细胞中均有表达;与SK通道在神经元细胞中介导动作电位后超极化过程的功能小同,在心房肌细胞中,SK通道是参与APs复极未期过程的重要离子通道.%To investigate the expression and functional role of the small conductance Ca2 +-activated K+ channels in human atrial myocytes. Methods We collected the right atrial appendage tissues from 8 patients with congenital heart defect with sinus rhythm undergoing open-heart surgery. Immunohistochemistry was performed to identify the expression of 3 isoforms of SK channel (SKI, SK2 and SK3). Using the classical two-step enzymatic isolation method, perforated patch clamp and conventional voltage-clamp techniques were performed to record the action potentials (Aps) and the whole-cell Ca2+-activated K+ current (Ik. C.) in the single atrial myocyte. We compared the changes in action potential duration (APD) before and after the application of a specific SK channels blocker apamin (100 nmol/L). Results Human atrial myocytes showed positivity for all the SKI, SK2 and SK3 isoform channels. Patch-clamp recording confirmed the presence of Ik,ca, and apamin significantly prolonged APD at 90% repolarization (APD90), but produced no obvious effect on APD50. Conclusion The three isoforms of SK channels are all expressed in human atrial myocytes. SK channels play a prominent role in the late phase of repolarization in human atrial myocytes, which is distinct from their functional roles in neurons where they mediate the process of afterhyperpolarization following Aps.