窦房结P细胞起搏的离子流机制研究进展

Research Progress of the Sinoatrial Node Cell′s Pacemaking Mechanism

窦房结是心脏正常起搏点，其自动电节律的机制是4期自动除极。因为参与4期除极的内向和外向离子流众多，加之实验动物种属、标本采集、细胞分离方法、灌流液成分和实验设备等多种因素的影响，研究结果尚不完全一致。目前公认的观点是：窦房结P细胞4期自动除极是多种离子流综合作用的结果：①窦房结起搏细胞高膜电阻；②衰减性钾电流（IK）；③背景内向钠电流（Ib-Na）；④钠-钙交换电流（INa-Ca）；⑤电压门控钙电流（ICa）；⑥超极化激活的内向离子流（If）。因为起搏细胞高膜电阻，在众多离子共同作用下引起4期除极速度达60～70 mV/s，成为心脏主导起搏细胞。

Sinoatrial node is the normal pacemaker of the heart. The mechanism of sinoatrial node＇s automatic electrical rhythmicity is 4 periods automatic depolarization. Because the multitudinous inward and outward ion current participate 4 periods depolarization and with other factors such as different race of animals ,specimen gathering ,the way of separate cell, the component of the fluid which was used to perfuse and the experiment equipments and so on, it leads to many divergence on the research result. At present the agreement of the viewpoint is：（1） High membranous resistance of the sinoatrial node＇s pacemaking cell;（2） Attenuate the electric current of the potassium（ IK ） ;（3） Background inward the electric current of the sodium（ Ib-Na ） ;（4） Sodium-calcium exchange electric current（ INa-Ca ） ;（5） The voltage gate controls the calcium electric current（ ICa） ;（6）The hyperpolarization activates inward ion stream（If）. Because the pacemaking cell＇s high membranous resistance, under the multitudinous ion＇s common action, the 4 period depolarization＇s speed can reach 60- 70 mV/s,it becomes the leading pacing cell of the heart.