The Ca2+-activated K+ channel and its functional roles in smooth muscle cells of guinea pig taenia coli.
The Ca2+-activated K+ channel and its functional roles in smooth muscle cells of guinea pig taenia coli.
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Ca2+激活的K+通道及其在豚鼠taenia大肠杆菌平滑肌细胞中的功能作用。
DOI：
10.1085/jgp.94.5.833
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发表时间：
1989-11
期刊：
影响因子：
--
通讯作者：
Kao CY
中科院分区：
文献类型：
--
作者：
Hu SL;Yamamoto Y;Kao CY
通过单个钾通道的电流进行了研究，在细胞贴附或由内而外补丁从胶原酶分散平滑肌细胞的豚鼠结肠带。在[K +] i = 135 mM：[K +] o = 5.4 mM的模拟生理状态的条件下，鉴定了三种不同类型的K+通道，其电导在0 mV附近为147、94和63 pS。94-和63-pS通道的活动很少观察到。147-pS通道最丰富。它的反向电位约为-75 mV。它对[Ca~（2+）] i和膜电位敏感。在-30 mV时，通道打开的概率最小。在更正的电压下，概率遵循玻尔兹曼分布。[Ca2 +] i的10倍变化导致电压负移25 mV，其中一半通道打开;当P较低时，膜电位的11.3 mV变化导致通道打开的概率增加e倍。在-30 mV和-50 mV之间的电压下，由于通道关闭时间大幅减少而通道打开时间没有太大变化，因此打开概率以异常方式增加。这种异常活动可能在维持静息电位中起调节作用。通道开放和关闭时间的直方图分别符合单指数分布和双指数分布。在通过100 ms脉冲阶跃去极化时，147 pS通道以短暂延迟打开。随着电位正性的增加，延迟时间缩短，开放通道的数量和开放时间增加。阶跃去极化过程中的平均电流非常类似于全细胞记录中的延迟整流外向K+电流。
Currents through single potassium channels were studied in cell- attached or inside-out patches from collagenase-dispersed smooth muscle cells of the guinea pig taenia coli. Under conditions mimicking the physiological state with [K+]i = 135 mM: [K+]o = 5.4 mM, three distinct types of K+ channel were identified with conductances around 0 mV of 147, 94, and 63 pS. The activities of the 94- and 63-pS channel were observed infrequently. The 147-pS channel was most abundant. It has a reversal potential of approximately -75 mV. It is sensitive to [Ca2+]i and to membrane potential. At -30 mV, the probability of a channel being open is at a minimum. At more positive voltages, the probability follows Boltzman distribution. A 10-fold change in [Ca2+]i causes a 25- mV negative shift of the voltage where half of the channels are open; an 11.3-mV change in membrane potential produces an e-fold increase in the probability of the channel being open when P is low. At voltages between -30 and -50 mV, the open probability increases in an anomalous manner because of a large decrease of the channel closed time without much change in the channel open time. This anomalous activity may play a regulatory role in maintaining the resting potential. The histograms of channel open and closed time fit well, respectively, with single and double exponential distributions. Upon step depolarizations by 100-ms pulses, the 147-pS channel opens with a brief delay. The delay shortens and both the number of open channels and the open time increase with increasing positivity of the potential. The averaged currents during the step depolarizations closely resemble the delayed rectifying outward K+ currents in whole-cell recordings.