Ionic permeation and blockade in Ca2+-activated K+ channels of bovine chromaffin cells.
Ionic permeation and blockade in Ca2+-activated K+ channels of bovine chromaffin cells.
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DOI：
10.1085/jgp.84.2.157
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发表时间：
1984-08
期刊：
影响因子：
--
通讯作者：
Yellen G
中科院分区：
文献类型：
--
作者：
Yellen G
通过牛嗜铬细胞的Ca 2+激活的K+通道的单通道电流进行测量，以确定通过通道的小离子渗透的影响。通道对K+的选择性强于Na+和Cs+，Rb+通过通道的电流比K+小。四乙基铵离子（TEA+）阻断通道电流时，适用于任何一侧的膜;它是有效的，在较低的浓度时，外部应用。内部Na+的毫摩尔浓度降低了通过通道的平均电流，并在开放通道电流中产生大的波动（闪烁）。这种闪烁块分析了一种新的方法，振幅分布分析，它可以测量块和未阻塞率在微秒的时间范围内，即使个别阻塞事件没有时间分辨的记录系统。分析表明，Na+阻断率与电压密切相关，而解除阻断率与电压无关。这些结果可以很容易地解释，通过假设，通过通道的电流是扩散限制，一个假设与单通道电流的大幅度一致。
Single channel currents through Ca2+-activated K+ channels of bovine chromaffin cells were measured to determine the effects of small ions on permeation through the channel. The channel selects strongly for K+ over Na+ and Cs+, and Rb+ carries a smaller current through the channel than K+. Tetraethylammonium ion (TEA+) blocks channel currents when applied to either side of the membrane; it is effective at lower concentrations when applied externally. Millimolar concentrations of internal Na+ reduce the average current through the channel and produce large fluctuations (flicker) in the open channel currents. This flickery block is analyzed by a new method, amplitude distribution analysis, which can measure block and unblock rates in the microsecond time range even though individual blocking events are not time-resolved by the recording system. The analysis shows that the rate of block by Na+ is very voltage dependent, but the unblock rate is voltage independent. These results can be explained easily by supposing that current flow through the channel is diffusion limited, a hypothesis consistent with the large magnitude of the single channel current.