INWARD RECTIFICATION IN THE TRANSVERSE TUBULAR SYSTEM OF FROG SKELETAL-MUSCLE STUDIED WITH POTENTIOMETRIC DYES
INWARD RECTIFICATION IN THE TRANSVERSE TUBULAR SYSTEM OF FROG SKELETAL-MUSCLE STUDIED WITH POTENTIOMETRIC DYES
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DOI：
10.1113/jphysiol.1985.sp015585
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发表时间：
1985-01-01
影响因子：
5.5
通讯作者：
VERGARA, J
中科院分区：
文献类型：
--
作者：
ASHCROFT, FM;HEINY, JA;VERGARA, J
使用非穿透电位染料 NK2367 和 WW375 研究内向整流对使用 3 凡士林间隙方法电压钳制的单蛙肌纤维的加权平均管状膜电位的影响。在 100 mM-K 溶液中，当超极化激活向内整流时，横向管状系统 (T 系统) 光信号的稳态振幅降低，其上升时间比等效去极化记录的上升时间更快。光衰减的电压依赖性遵循内向整流，并且随着超极化的增加而增加。对于 -140 mV 的电压钳位，光衰减为 0.72，对应于 100 mV 的加权平均 T 系统电势变化。当内向整流在 Cs、TEA [四乙基铵] 溶液中被阻断时，光学衰减也被消除。含有低浓度 Cs 的溶液中内向电流阻断的电压依赖性也反映在 T 系统光信号中。 T系统的径向电缆模型，假设表面和管状膜中具有相同的特定向内整流器电导，预测所测量的光学衰减对应于管状空间常数λT的减小，从无源条件下的120μm减少到约100μm。内向整流完全激活时为 40 .mu.m。通过假设比电导服从玻尔兹曼型电压依赖性，可以很好地预测在表面膜上测量的内向整流的电压依赖性；管减少的主要影响是降低总（表面+ T 系统）电导-电压关系的陡度。
The non-penetrating potentiometric dyes NK2367 and WW375 were used to investigate the effect of inward rectification on the weighted-average tubular membrane potential in single frog muscle fibers voltage clamped using a 3 Vaseline-gap method. In 100 mM-K solution, when inward rectification was activated by hyperpolarization the steady-state amplitude of the transverse tubular system (T-system) optical signal was reduced and its rise time was faster than that recorded for an equivalent depolarization. The voltage dependence of the optical attenuation followed that of inward rectification, increasing with increasing hyperpolarization. For a voltage-clamp step of -140 mV the optical atenuation was 0.72 which correspondes to a weighted-average T-system potential change of 100 mV. When inward rectification was blocked in a Cs, TEA [tetra ethyl-ammoinum] solution the optical attenuation was also abolished. The voltage dependence of the block of the inward currents in solutions containing low concentrations of Cs was also reflected in the T-system optical signals. A radial cable model of the T-system, assuming the same specific inward rectifier conductance in surface and tubular membranes predicted that the measured optical attenuation corresponds to a decrease in the tubular space constant, .lambda.T, from 120 .mu.m under passive conditions to .apprx. 40 .mu.m when inward rectification is fully activated. The voltage dependence of inward rectification measured at the surface membrane was reasonably well predicted by assuming that the specific conductance obeyed a Boltzmann type of voltage dependence; that major effect of tubular decrements was to reduce the steepness of the total (surface + T-system) conductance-voltage relation.