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本文应用全细胞膜片钳记录技术、可视化动缘探测系统及细胞内钙测定系统和多道生理信号采集处理系统,研究藜芦定(veratridine,VER)对家兔心室肌细胞持续钠电流(persistent sodium current,INa.P)、Na+/Ca2+交换电流(Na+/Ca2+exchange current,INCX)、钙瞬变及动作电位(action potential,AP)的影响,并探讨其引起细胞内Ca2+超载和增强心肌收缩的发生机制。结果显示,给予心室肌细胞10、20μmol/LVER后,INa.P和反向INCX电流密度均增大,再加入4μmol/L河豚毒素(tetrodotoxin,TTX)后,INa.P和反向INCX电流密度均又明显减小。在另一组实验中,特异性INa.P阻断剂雷喏嗪(ranolazine,RAN)也明显抑制由VER诱导增大的INa.P和反向INCX。加入2.5μmol/LVER后,心室肌细胞最大收缩速率、收缩幅度和钙瞬变基线(舒张期Ca2+浓度)均增大,加入2μmol/LTTX后上述三项指标均明显减小。VER(20μmol/L)可使心室肌细胞AP复极至50%(action potential duration at 50% repolarization,APD50)和90%的时间(action potential duration at 90% repolarization,APD90)延长,其中3例出现早期后除极(early after depolarizations,EADs),加入4μmol/LTTX后APD50、APD90均明显缩短,3例EADs均消失。实验结果提示:(1)VER作为特异性INa.P的开放剂,可引起心室肌细胞INa.P增大而产生细胞内Na+超载,继而通过反向INCX的增大导致细胞内Ca2+超载。(2)由VER诱导增大的心室肌细胞INa.P还可引起心室肌细胞APD延长,诱发EADs。(3)TTX对由VER引起的上述指标的异常变化均有明显抑制作用,说明上述指标的异常变化是由INa.P增大所引起。以上结果表明,VER作为INa.P的开放剂,通过增大INa.P而引起反向INCX增强,最终导致细胞内Ca2+超载和APD异常延长。
In this paper, whole-cell patch clamp recording technology, visualization of kinetic detection system and intracellular calcium assay system and multi-channel physiological signal acquisition and processing system, veratridine (veratridine, VER) on persistent sodium current in rabbit ventricular myocytes current, INa.P), Na + / Ca2 + exchange current (INCX), calcium transients and action potentials (APs), and to investigate their effects on intracellular Ca2 + overload and myocardial contractility The mechanism of occurrence. The results showed that after administration of 10 and 20μmol / LVER, the current density of INa.P and reverse INCX both increased. After addition of 4μmol / L tetrodotoxin (TTX), the current density of INa.P and reverse INCX Both were significantly reduced. In another set of experiments, the specific INa.P blocker ranolazine (RAN) also significantly inhibited the increased INa.P induced by VER and the reverse INCX. After adding 2.5μmol / LVER, the maximum contraction rate, contraction amplitude and calcium transient baseline (diastolic Ca2 + concentration) of ventricular myocytes increased, and the above three indexes were significantly decreased after adding 2μmol / LTTX. VER (20μmol / L) could prolong APD50 and APD90 in 50% of ventricular myocytes, of which 3 appeared Early after depolarizations (EADs), APD50 and APD90 were significantly shortened after addition of 4μmol / LTTX, and all three cases of EADs disappeared. The experimental results suggest that: (1) VER, as a specific INa.P opener, can induce intracellular Na + overload by increasing INa.P of ventricular myocytes, and then lead to overloading of intracellular Ca2 + by increasing reverse INCX. (2) INa.P induced by VER increased ventricular myocytes APD can also cause prolonged induced EADs. (3) TTX significantly inhibited the abnormal changes of the above indexes induced by VER, indicating that the abnormal changes of these indexes are caused by the increase of INa.P. The above results indicate that VER acts as an opener for INa.P and increases reverse INCX by increasing INa.P, eventually leading to intracellular Ca2 + overload and abnormal prolongation of APD.