UNIDIRECTIONAL SODIUM AND POTASSIUM FLUXES THROUGH THE SODIUM-CHANNEL OF SQUID GIANT-AXONS
UNIDIRECTIONAL SODIUM AND POTASSIUM FLUXES THROUGH THE SODIUM-CHANNEL OF SQUID GIANT-AXONS
复制标题
DOI：
10.1016/s0006-3495(82)84456-1
复制
发表时间：
1982-01-01
影响因子：
3.4
通讯作者：
BEGENISICH, T
中科院分区：
文献类型：
--
作者：
BUSATH, D;BEGENISICH, T
单向22钠示踪钠内流或42 K示踪钾流出跨膜电压钳鱿鱼巨轴突在不同的膜电位下双离子条件下进行了测量。河豚毒素几乎完全消除了额外的K+外流诱导的短重复去极化在四乙基铵或3，4-二氨基吡啶的存在下。本文描述了一种测定通过电压门控通道的单向通量的电压依赖性的方法。这种技术被用来获得单向的流量-电压关系的Na通道在双离子和单离子的条件。它允许在零电流电势下确定单向通量，对于inlux，该电势为apx。测量值的20%为80 mV负向零电流电位。还测量了双离子条件下的单向通量比，外部Na溶液和内部K溶液的通量比指数平均为1.15。一个3-障碍，2-网站，多占用模型先前获得的其他条件下预测一个类似的非统一的平均通量比指数。一些单占据模型可以预测双离子条件下通量比指数的非统一值。
Unidirectional 22Na-traced Na influx or 42K-traced K efflux across the membranes of voltage-clamped squid giant axons was measured at various membrane potentials under bi-ionic conditions. Tetrodotoxin almost entirely eliminated the extra K+ efflux induced by short repetitive depolarizations in the presence of tetraethylammonium or 3,4-diaminopyridine. A method of detering the voltage dependence of the unidirectional flux through voltage-gated channels is described. This technique was used to obtain the unidirectional flux-voltage relation for the Na channel in bi-ionic and single-ion conditions. It allows the determination of the unidirectional flux at the zero-current potential which, for inlux, was .apprx. 20% of the value measured 80 mV negative to the zero-current potential. The unidirectional flux ratio under bi-ionic conditions was also measured and the flux ratio exponent averaged 1.15 with an external Na solution and an internal K solution. A 3-barrier, 2-site, multi-occupancy model previously obtained for other conditions predicted a similar non-unity average for the flux ratio exponent. Some single-occupancy models can predict non-unity values for the flux ratio exponent in bi-ionic conditions.