Toro L, González-Robles A, Stefani E
Am J Physiol. 1986 Nov;251(5 Pt 1):C763-73. doi: 10.1152/ajpcell.1986.251.5.C763.
Single vascular smooth muscle cells (VSMC) were isolated from the caudal artery and vein and studied after 2 or 3 days in culture. Current clamp with intracellular microelectrodes and "whole-cell" voltage-clamp techniques were used. Also, scanning and transmission electron microscopy studies were performed, revealing morphological characteristics of smooth muscle in culture. Cells could contract in response to electrical and chemical stimuli. The passive membrane properties recorded with intracellular microelectrodes in a mammalian saline were as follows: 1) for artery, resting potential Vm = -56 +/- 5 mV (mean +/- SD), input resistance Rin = 590 +/- 35 M omega, membrane time constant tau m = 19 +/- 2 ms, membrane capacity C/cm2 = 1.3 +/- 0.2 microF/cm2, and length constant lambda = 900 +/- 40 micron; and 2) for vein, Vm = -66 +/- 3 mV, Rin = 450 +/- 25 M omega, tau m = 19 +/- 2 ms, C/cm2 = 1.0 +/- 0.1 microF/cm2, and lambda = 1,300 +/- 200 micron. The values calculated for a short cable and the observed change of the membrane potential as a single exponential, in response to hyperpolarizing pulses of current, both indicate that the cell membrane behaves as an isopotential surface. With hyperpolarizing pulses, both cell types gave linear voltage-current (V-I) relationships with a constant slope, Rin. On the other hand, depolarizing pulses elicited outward rectification. Voltage-clamp experiments show an outward voltage-dependent K+ current (IK) when the cell membrane is depolarized beyond approximately equal to -40 mV from holding levels approximately equal to -60 mV. Maximum slope conductances were of approximately 120 microS/cm2. Blocking of K+ channels with tetraethylammonium ions did not unmask an inward current. These results indicate that VSMC from rat caudal artery and vein in culture have K+ channels responsible for the graded depolarization of the cell membrane in response to an electrical stimulus. Furthermore, this experimental approach seems to be adequate to further study the electrical responses of VSMC from vessels at distinct stages of development, and to follow these responses as the cells change in a defined environment.
从尾动脉和尾静脉分离出单个血管平滑肌细胞（VSMC），并在培养2或3天后进行研究。采用细胞内微电极电流钳和“全细胞”电压钳技术。此外，还进行了扫描和透射电子显微镜研究，揭示了培养的平滑肌的形态特征。细胞可对电刺激和化学刺激产生收缩反应。在哺乳动物盐溶液中用细胞内微电极记录的被动膜特性如下：1）对于动脉，静息电位Vm = -56±5 mV（平均值±标准差），输入电阻Rin = 590±35 MΩ，膜时间常数τm = 19±2 ms，膜电容C/cm2 = 1.3±0.2 μF/cm2，长度常数λ = 900±40 μm；2）对于静脉，Vm = -66±3 mV，Rin = 450±25 MΩ，τm = 19±2 ms，C/cm2 = 1.0±0.1 μF/cm2，λ = 1300±200 μm。根据短电缆计算的值以及响应超极化电流脉冲时膜电位作为单指数的观察变化，均表明细胞膜表现为等电位表面。对于超极化脉冲，两种细胞类型均给出具有恒定斜率Rin的线性电压-电流（V-I）关系。另一方面，去极化脉冲引起外向整流。电压钳实验表明，当细胞膜从约-60 mV的钳制水平去极化超过约-40 mV时，存在外向电压依赖性钾电流（IK）。最大斜率电导约为120 μS/cm2。用四乙铵离子阻断钾通道并未揭示内向电流。这些结果表明，培养的大鼠尾动脉和尾静脉VSMC具有钾通道，这些通道负责细胞膜对电刺激的分级去极化反应。此外，这种实验方法似乎足以进一步研究处于不同发育阶段的血管VSMC的电反应，并在细胞在特定环境中发生变化时追踪这些反应。
