Heiny J A, Jong D S
Department of Physiology and Biophysics, University of Cincinnati, College of Medicine, Ohio 45267-0576.
J Gen Physiol. 1990 Jan;95(1):147-75. doi: 10.1085/jgp.95.1.147.
Voltage-sensing dyes were used to examine the electrical behavior of the T-system under passive recording conditions similar to those commonly used to detect charge movement. These conditions are designed to eliminate all ionic currents and render the T-system potential linear with respect to the command potential applied at the surface membrane. However, we found an unexpected nonlinearity in the relationship between the dye signal from the T-system and the applied clamp potential. An additional voltage- and time-dependent optical signal appears over the same depolarizing range of potentials where change movement and mechanical activation occur. This nonlinearity is not associated with unblocked ionic currents and cannot be attributed to lack of voltage clamp control of the T-system, which appears to be good under these conditions. We propose that a local electrostatic potential change occurs in the T-system upon depolarization. An electrostatic potential would not be expected to extend beyond molecular distances of the membrane and therefore would be sensed by a charged dye in the membrane but not by the voltage clamp, which responds solely to the potential of the bulk solution. Results obtained with different dyes suggest that the location of the phenomena giving rise to the extra absorbance change is either intramembrane or at the inner surface of the T-system membrane.
电压敏感染料被用于在类似于通常用于检测电荷运动的被动记录条件下检查T系统的电行为。这些条件旨在消除所有离子电流，并使T系统电位相对于施加在表面膜上的指令电位呈线性关系。然而，我们发现T系统的染料信号与施加的钳制电位之间的关系存在意外的非线性。在发生电荷运动和机械激活的相同去极化电位范围内，会出现一个额外的电压和时间依赖性光学信号。这种非线性与未阻断的离子电流无关，也不能归因于T系统电压钳制控制的不足，在这些条件下T系统的电压钳制控制似乎是良好的。我们提出，去极化时T系统中会发生局部静电电位变化。静电电位预计不会延伸到膜的分子距离之外，因此会被膜中的带电染料检测到，但不会被仅对本体溶液电位作出响应的电压钳检测到。用不同染料获得的结果表明，引起额外吸光度变化的现象发生位置要么在膜内，要么在T系统膜的内表面。
