Bolzon B J, Xiong Z, Cheung D W
University of Ottawa Heart Institute, Canada.
Pflugers Arch. 1993 Dec;425(5-6):482-90. doi: 10.1007/BF00374875.
Membrane rectification to depolarization was studied by voltage recording with patch electrodes in freshly isolated cells from the rat tail artery. Injection of depolarizing currents elicited electrotonic potentials that developed with a single-exponential time course (time constant of 94.8 ms). When the cell was depolarized beyond -30 mV, delayed rectification was observed. A second type of rectification, characterized by oscillations, was observed when the cell was depolarized positive to +30 mV. The threshold of this rectification and the oscillations were sensitive to changes in intracellular Ca2+. Delayed rectification was more sensitive to 4-aminopyridine but more resistant to tetraethylammonium and charybdotoxin than the Ca(2+)-sensitive rectification. A 4-aminopyridine-sensitive outward current (IK,dr) with a threshold of around -30 mV and a second Ca(2+)-sensitive outward current (IK,Ca) activated at around +30 mV were observed from whole-cell voltage clamp recordings. IK,Ca was blocked by tetraethylammonium and charybdotoxin. An 11-pS and a 122-pS channel, having characteristics similar to IK,dr and IK,Ca respectively, were identified from single-channel recordings. These observations showed how membrane depolarization of vascular smooth-muscle cells was regulated by these two populations of K+ channels under various conditions.
采用膜片钳电极电压记录法，对新鲜分离的大鼠尾动脉细胞的膜去极化整流进行了研究。注入去极化电流可诱发以单指数时间进程发展的电紧张电位（时间常数为94.8毫秒）。当细胞去极化超过-30 mV时，可观察到延迟整流。当细胞去极化至+30 mV以上时，观察到另一种以振荡为特征的整流类型。这种整流的阈值和振荡对细胞内Ca2+的变化敏感。与Ca(2+)敏感整流相比，延迟整流对4-氨基吡啶更敏感，但对四乙铵和蝎毒素更具抗性。从全细胞膜片钳记录中观察到一种阈值约为-30 mV的4-氨基吡啶敏感外向电流（IK,dr）和一种在约+30 mV激活的第二种Ca(2+)敏感外向电流（IK,Ca）。IK,Ca被四乙铵和蝎毒素阻断。从单通道记录中鉴定出一个11-pS和一个122-pS的通道，其特性分别类似于IK,dr和IK,Ca。这些观察结果表明，在各种条件下，这两种钾通道如何调节血管平滑肌细胞的膜去极化。
