肾上腺髓质瘤无性繁殖细胞膜上的异常整流钾通道

作者用斑片钳技术,在传代培养的大鼠肾上腺髓质瘤无性繁殖细胞(PC12 cell)膜上记录电压依赖性钾离子通道活动。观察到两种超极化时激活的内向离子流,电导为30～60皮西门(PS)及大于100 pS。电导大的通道活动常呈大的闪动样关闭及簇状猝发。电导30～60 pS的钾通道具有如下特征:①明显的电压依赖性。在膜超极化到阈电位水平(30 mV)时,通道开放。同一电压下,单通道电流幅度基本一致,呈正态分布。不同钳位电压下,随着超极化程度增大,电流幅度渐增大。②平均开放时间和开放概率随超极化程度增大而增大,关闭时间则随之而减小。③I-V曲线上显示翻转电位接近K~ 的平衡电位。④钾通道阻断剂TEA能阻断该通道。

A SINGLE ANOMALOUS RECTIFICATION POTASSIUM CHANNEL IN PHEOCHRO- MOCYTOMA(PC12) CELLS

Single channel recording using the patch-clamp technique was carried out on the membrane of the passaged cultured clonal pheochromocytoma cells. Hyperpolarizing voltage steps activated inward directed single-channel currents with conductance 30~60 pS and above 100 pS. The channel activities with large conductance exhibited flickering and bursting. The properties of the 30-60 pS potassium channels are as following: (1) The channel opened when the membrane was hyperpolarized at threshold (30mV). In a given hyperlarizing voltage, the channel current has a unitary amplitude and a normal distribution histogram. Its current amplitude increased when hyperpolarization incresed. (2) In the voltage range studied, open time, open probability increased and closed time reduced when byperpolarization increased. (3) I-V curve revealed that the reversal membrane potential closed to the K equilibrium potential. (4)The current amplitude could be blocked by potassium channel blocker TEA.