Mathers D A, Zhang X
Department of Physiology, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
Biochim Biophys Acta. 1995 May 24;1236(1):89-94. doi: 10.1016/0005-2736(95)00033-y.
Inside-out patch clamp recordings have revealed the presence of a novel, large conductance channel of the non-selective, cation permeable type in smooth muscle cells dispersed from the cerebral arteries of adult rats. In physiologically appropriate ionic gradients, current flow in these channels reversed polarity at a membrane potential of about -42 mV. Single channel conductance in symmetrical 140 mM K+ salines was 211 pS. The channel was permeable to both K+ and Na+, with a ratio PNa/PK = 0.15, while Cl- was effectively impermeant. Calcium ions were weakly permeant (PCa/PK = 0.03, PCa/PNa = 0.20). Channel open probability increased with membrane depolarization and was weakly dependent on the concentration of free intracellular Ca2+. This channel would contribute outward membrane current at potentials more positive than about -42 mV. In concert with outward potassium currents, it may serve to limit membrane depolarization during action potential activity in cerebrovascular smooth muscle cells.
外向膜片钳记录显示，从成年大鼠脑动脉分离出的平滑肌细胞中存在一种新型的、大电导的非选择性阳离子通透通道。在生理合适的离子梯度下，这些通道中的电流在约 -42 mV 的膜电位处反转极性。在对称的 140 mM K⁺ 盐溶液中，单通道电导为 211 pS。该通道对 K⁺ 和 Na⁺ 均通透，PNa/PK 比值为 0.15，而 Cl⁻ 实际上是不通透的。钙离子通透性较弱（PCa/PK = 0.03，PCa/PNa = 0.20）。通道开放概率随膜去极化增加，且对细胞内游离 Ca²⁺ 浓度的依赖性较弱。在电位高于约 -42 mV 时，该通道会产生外向膜电流。与外向钾电流协同作用，它可能有助于限制脑血管平滑肌细胞动作电位活动期间的膜去极化。
