Voltage-sensitive and solvent-sensitive processes in ion channel gating. Kinetic effects of hyperosmolar media on activation and deactivation of sodium channels.
Voltage-sensitive and solvent-sensitive processes in ion channel gating. Kinetic effects of hyperosmolar media on activation and deactivation of sodium channels.
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离子通道门控中的电压敏感和溶剂敏感过程。
DOI：
10.1016/s0006-3495(92)81819-2
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发表时间：
1992
影响因子：
3.4
通讯作者：
Alicata,DA
中科院分区：
文献类型：
--
作者：
Rayner,MD;Starkus,JG;Ruben,PC;Alicata,DA
研究了用氯胺-T去除快速失活后渗透应激对小龙虾巨轴突钠离子电流和门控电流的动力学影响。通过添加甲酰胺或蔗糖制成高渗性培养基的内部灌注降低了峰值钠电流（在用氯胺-T去除快速失活之前和之后），增加了活化的半衰期，但对尾电流失活率没有影响。ON和OFF门控电流的动力学不受渗透胁迫的影响。这些结果证实了（并扩展到钠通道）最近由Zimmerberg J.提出的将通道门控机制分离为电压敏感性和溶剂敏感性过程，F. Bezanilla和V.A.帕斯吉安（1990年。Biophys. J. 57：1049-1064）用于钾延迟整流通道。此外，高渗介质产生的动力学效应似乎与淡水螯虾轴突中重水替代的动力学效应定性相似（Alicata，D.一、M. D. Rayner和J.G.斯塔克斯1990. Biophys. J. 57：745-758）。然而，我们的观察是不兼容的模型，其中电压敏感和溶剂敏感的门控过程被假定为（a）严格顺序或（B）平行和独立的。我们介绍了一个变种的并行模型，其中包括明确的电压敏感和溶剂敏感的过程之间的耦合。该模型的模拟，其中总耦合能小至1/10千吨，证明了我们的数据中指出的特征动力学变化。
Kinetic effects of osmotic stress on sodium ionic and gating currents have been studied in crayfish giant axons after removal of fast inactivation with chloramine-T. Internal perfusion with media made hyperosmolar by addition of formamide or sucrose, reduces peak sodium current (before and after removal of fast inactivation with chloramine-T), increases the half-time for activation, but has no effect on tail current deactivation rate(s). Kinetics of ON and OFF gating currents are not affected by osmotic stress. These results confirm (and extend to sodium channels) the separation of channel gating mechanisms into voltage-sensitive and solvent-sensitive processes recently proposed by Zimmerberg J., F. Bezanilla, and V. A. Parsegian. (1990. Biophys. J. 57:1049–1064) for potassium delayed rectifier channels. Additionally, the kinetic effects produced by hyperosmolar media seem qualitatively similar to the kinetic effects of heavy water substitution in crayfish axons (Alicata, D. A., M. D. Rayner, and J. G. Starkus. 1990. Biophys. J. 57:745–758). However, our observations are incompatible with models in which voltage-sensitive and solvent-sensitive gating processes are presumed to be either (a) strictly sequential or, (b) parallel and independent. We introduce a variant of the parallel model which includes explicit coupling between voltage-sensitive and solvent-sensitive processes. Simulations of this model, in which the total coupling energy is as small as 1/10th of kT, demonstrate the characteristic kinetic changes noted in our data.