Permeation and interaction of divalent cations in calcium channels of snail neurons.
Permeation and interaction of divalent cations in calcium channels of snail neurons.
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蜗牛神经元钙通道中二价阳离子的渗透和相互作用。
DOI：
10.1085/jgp.85.4.491
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发表时间：
1985-04
期刊：
影响因子：
--
通讯作者：
Stimers JR
中科院分区：
文献类型：
--
作者：
Byerly L;Chase PB;Stimers JR
本文研究了不同二价阳离子对滞水蛙神经元钙通道的载流能力和阻断作用。改变渗透的二价阳离子的浓度或种类以与二价阳离子对外表面电势的作用一致的方式改变Ca通道电流的激活的电压依赖性。增加渗透阳离子的浓度从1到30 mM产生的最大钙电流的两倍增加和最大钡电流的四倍增加;最大钡电流的两倍大小的最大钙电流为10 mM的散装浓度。校正由门控机制看到的变化的表面电位，电流-浓度关系对于Ba 2+几乎是线性的，并且对于Ca 2+仅显示出中等饱和;此外，发现Ca 2+、Ba 2+和Sr 2+几乎同样好地通过通道。这些结论是在以下两种假设下得出的：通道口（a）看到门控机构看到的所有表面电势，或（B）没有看到门控机构看到的表面电势。Cd 2+在比Co2+或Ni 2+所需的浓度小200倍的浓度下阻断了双孢霉和HischiaCa通道。Ca 2+与Cd 2+竞争阻断位点; Ba 2+与该位点的结合强度低于Ca 2+。Ca ~（2+）和Ba ~（2+）的混合物对Ca通道电流产生异常的摩尔分数效应。在对变化的表面电位进行校正后（使用任一假设），异常摩尔分数效应甚至更加突出，这表明Ba 2+对Ca电流的阻断大于Ca 2+对Ba电流的阻断。
We have studied the current-carrying ability and blocking action of various divalent cations in the Ca channel of Lymnaea stagnalis neurons. Changing the concentration or species of the permeant divalent cation shifts the voltage dependence of activation of the Ca channel current in a manner that is consistent with the action of the divalent cation on an external surface potential. Increasing the concentration of the permeant cation from 1 to 30 mM produces a twofold increase in the maximum Ca current and a fourfold increase in the maximum Ba current; the maximum Ba current is twice the size of the maximum Ca current for 10 mM bulk concentration. Correcting for the changing surface potential seen by the gating mechanism, the current- concentration relation is almost linear for Ba2+, and shows only moderate saturation for Ca2+; also, Ca2+, Ba2+, and Sr2+ are found to pass through the channel almost equally well. These conclusions are obtained for either of two assumptions: that the mouth of the channel sees (a) all or (b) none of the surface potential seen by the gating mechanism. Cd2+ blocks Lymnaea and Helix Ca channels at concentrations 200 times smaller than those required for Co2+ or Ni2+. Ca2+ competes with Cd2+ for the blocking site; Ba2+ binds less strongly than Ca2+ to this site. Mixtures of Ca2+ and Ba2+ produce an anomalous mole fraction effect on the Ca channel current. After correction for the changing surface potential (using either assumption), the anomalous mole fraction effect is even more prominent, which suggests that Ba2+ blocks Ca current more than Ca2+ blocks Ba current.