SODIUM-CHANNEL PERMEATION IN SQUID AXONS .1. REVERSAL POTENTIAL EXPERIMENTS
SODIUM-CHANNEL PERMEATION IN SQUID AXONS .1. REVERSAL POTENTIAL EXPERIMENTS
复制标题
DOI：
10.1113/jphysiol.1980.sp013432
复制
发表时间：
1980-01-01
影响因子：
5.5
通讯作者：
CAHALAN, MD
中科院分区：
文献类型：
--
作者：
BEGENISICH, TB;CAHALAN, MD
在电压钳制的鱿鱼巨轴突上研究了钠通道的翻转电位。离子选择性的浓度依赖性确定与外部和内部的Na和NH 4浓度的变化。内部NH 4活性的10倍变化导致反转电位的42 mV偏移，而不是对于恒定PNa/PNH 4比率的Goldman、Hodgkin、Katz方程预期的56 mV偏移。在恒定的内部[NH 4]下，将[Na]0改变10倍，得到约56 mV的预期位移。表观通道选择性取决于内部NH 4浓度，而不是外部Na浓度。NH 4外，钠内，计算的渗透率比几乎是恒定的，无论渗透离子浓度。内部Cs离子可以改变Na/K渗透率比。结果被认为是在3-障碍，2-网站离子渗透模型。
Na channel reversal potentials were studied in perfused voltage clamped squid giant axons. The concentration dependence of ion selectivity was determined with external and internal changes in Na and NH4 concentrations. A 10-fold change in the internal NH4 activity results in a 42 mV shift in the reversal potential, rather than the 56 mV shift expected from the Goldman, Hodgkin, Katz equation for a constant PNa/PNH4 ratio. Changing [Na]0 10-fold at constant internal [NH4] gives approximately the expected 56 mV shift. The apparent channel selectivity depends upon the internal NH4 concentration but not the external Na concentration. With NH4 outside and Na inside, the calculated permeability ratio is nearly constant, regardless of the permeant ion concentration. Internal Cs ions can alter the Na/K permeability ratio. The results are considered in terms of 3-barrier, 2-site ionic permeation model.