Inward current in single smooth muscle cells of the guinea pig taenia coli.
Inward current in single smooth muscle cells of the guinea pig taenia coli.
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DOI：
10.1085/jgp.93.3.521
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发表时间：
1989-03
期刊：
影响因子：
--
通讯作者：
Kao CY
中科院分区：
文献类型：
--
作者：
Yamamoto Y;Hu SL;Kao CY
本文用密闭电压钳方法研究了酶分散的豚鼠结肠带平滑肌细胞的离子电流。在含有3 mM Ca 2+的生理培养基中，细胞呈逐渐变细的纺锤体，平均201（长度）x 8微米（细胞中心的最大直径），体积为5 μ l。平均电池电容为50 pF，比膜电容为1.15 microF/cm 2。静息细胞的输入阻抗为1-2 G Ω。在第一个400微秒之后，空间均匀的电压控制占主导地位。内向电流和外向电流有很多重叠，但内向电流可以通过内部施加Cs+来阻断所有钾电流而被隔离。内向电流由Ca 2+携带。激活开始于约-30 mV，最大伊卡发生在+10-+20 mV，反转电位约为+75 mV。Ca ~（2+）通道对Sr ~（2+）和Ba ~（2+）有渗透性，对Cs ~+有渗透性，但对Na ~+无渗透性。激活和失活是非常迅速的，在约33摄氏度，与时间常数小于1毫秒。失活有一个复杂的时间过程，可分解成三个指数分量，平均时间常数（在0 mV）为7，45，和400毫秒，这是不同的电压影响。对于所有组合的组分，稳态失活在-30 mV下为半最大值，但对于快速组分为-36 mV，对于其他两种组分为-26 mV和-23 mV。多种形式的Ca 2+通道的存在是从失活特征推断的，而不是从激活特性推断的。快通道的恢复以72 ms的时间常数（+10 mV）发生。在动作电位期间的Ca 2+内流可以转移大约9 pC的电荷，这可以充分提高细胞内Ca 2+浓度以用于各种生理功能。
Using the tight-seal voltage-clamp method, the ionic currents in the enzymatically dispersed single smooth muscle cells of the guinea pig taenia coli have been studied. In a physiological medium containing 3 mM Ca2+, the cells are gently tapering spindles, averaging 201 (length) x 8 microns (largest diameter in center of cell), with a volume of 5 pl. The average cell capacitance is 50 pF, and the specific membrane capacitance 1.15 microF/cm2. The input impedance of the resting cell is 1-2 G omega. Spatially uniform voltage-control prevails after the first 400 microseconds. There is much overlap of the inward and outward currents, but the inward current can be isolated by applying Cs+ internally to block all potassium currents. The inward current is carried by Ca2+. Activation begins at approximately -30 mV, maximum ICa occurs at +10-+20 mV, and the reversal potential is approximately +75 mV. The Ca2+ channel is permeable to Sr2+ and Ba2+, and to Cs+ moving outwards, but not to Na+ moving inwards. Activation and deactivation are very rapid at approximately 33 degrees C, with time-constants of less than 1 ms. Inactivation has a complex time course, resolvable into three exponential components, with average time constants (at 0 mV) of 7, 45, and 400 ms, which are affected differently by voltage. Steady- state inactivation is half-maximal at -30 mV for all components combined, but -36 mV for the fast component and -26 and -23 mV for the other two components. The presence of multiple forms of Ca2+ channel is inferred from the inactivation characteristics, not from activation properties. Recovery of the fast channel occurs with a time-constant of 72 ms (at +10 mV). Ca2+ influx during an action potential can transfer approximately 9 pC of charge, which could elevate intracellular Ca2+ concentration adequately for various physiological functions.