槐果碱抗心律失常的电生理机制研究

Study on the electrophysiological mechanism of sophocarpine against arrhythmia

目的探讨槐果碱对心肌细胞动作电位(action potentials,AP)及离子电流的电生理效应。方法将豚鼠心脏快速取出后通过心电图记录心脏对槐果碱的应答;采用常规微电极技术对豚鼠乳头状肌或兔窦房结细胞快反应及慢反应动作电位进行记录,研究槐果碱的相关效应;获取新生大鼠心室心肌细胞进行原代培养,采用膜片钳技术记录全细胞及单通道电流;采用穿孔膜片钳技术进行全细胞钙流记录。结果在异丙肾上腺素诱导后出现心动过速,而槐果碱(300μmol)加入后,心动过速或室颤现象消失,心电图提示出现正常心跳。对于豚鼠心室心肌细胞的快反应动作电位,槐果碱作用后,APD及动作电位的有效不应期延长,APA下降。对于窦房结的慢反应动作电位,槐果碱处理后,APA及Vmax均出现下降,且APD90也能够延长。结果显示槐果碱通过阻断I_(kr)而非I_(ks)实现对APD的延长。新生大鼠心室细胞的细胞电流实验结果显示10μmol/L槐果碱能够导致I_(Na)下降约18%。且槐果碱能够在全体细胞水平上降低慢内向电流,尾部电流(外向K+电流)也出现消失,相比于对照组,I_(CaL)在20 m V指令电位时,平均减少(33.2±11.7)%。结论槐果碱能够逆转异丙肾上腺素引起的心律失常,其作用机制为抑制Na离子、钙离子及钾离子电流。

Objective To investigate the electrophysiological effects of sophocarpine on cardiomyocyte action potentials （AP） and ion currents. Methods The heart of guinea pigs was quickly removed and response of heart to sophocarpine was recorded by electrocardiogram. The conventional microelectrode technique was used to record the fast response and slow response action potentials of guinea pig papillary muscles or rabbit sinoatrial node cells, and the related effects of sophocarpine were investigated; neonatal rat ventricular cardiomyocytes were obtained for primary culture. Patch-clamp technique was used to record whole-cell and single-channel currents; perforated patch-clamp technique was used to record whole-cell calcium flow. Results Tachycardia occurred after isoproterenol induction, and after sophocarpine（300 I^mol） was added, tachycardia or ventricular fibrillation disappeared. Electrocardiogram indicated a normal heartbeat. For ventricular cardiomyocytes fast response action potential in guinea pigs, after the sophocarpine was given, the effec- tive refractory period of APD and action potential was prolonged, and APA was decreased. For the slow response action potential of the sinus node, after sophocarpine was given, APA and Vmax were both decreased. APD90 could also be prolonged. The results showed that sophocarpine extended APD by blocking Ikr instead of Iks. The experimental results of cell currents in neonatal rat ventricular cells showed that 10 μmol/L sophocarpine could cause INa to decrease by about 18%. Moreover, sophocarpine could reduce the slow inward current at the whole cell level. Tail current（outward K＋ current） also disappeared. LCaL was decreased by an average of （33.2±11.7）% at a 20 mV command potential compared to the control group. Conclusion Sophoearpine can reverse isoproterenol - induced arrhythmia. Its mechanism of action is to inhibit the currents of Na＊, Ca2. and K^＋.