Wilders R, Jongsma H J
Department of Physiology, University of Amsterdam, The Netherlands.
Biophys J. 1992 Oct;63(4):942-53. doi: 10.1016/S0006-3495(92)81664-8.
The electrical properties of gap junctions in cell pairs are usually studied by means of the dual voltage clamp method. The voltage across the junctional channels, however, cannot be controlled adequately due to an artificial resistance and a natural resistance, both connected in series with the gap junction. The access resistances to the cell interior of the recording pipettes make up the artificial resistance. The natural resistance consists of the cytoplasmic access resistances to the tightly packed gap junction channels in both cells. A mathematical model was constructed to calculate the actual voltage across each gap junction channel. The stochastic open-close kinetics of the individual channels were incorporated into this model. It is concluded that even in the ideal case of complete compensation of pipette series resistance, the number of channels comprised in the gap junction may be largely underestimated. Furthermore, normalized steady-state junctional conductance may be largely overestimated, so that transjunctional voltage dependence is easily masked. The model is used to discuss conclusions drawn from dual voltage clamp experiments and offers alternative explanations for various experimental observations.
通常采用双电压钳法研究细胞对中缝隙连接的电学特性。然而，由于与缝隙连接串联的人工电阻和自然电阻，跨连接通道的电压无法得到充分控制。记录微电极进入细胞内部的电阻构成人工电阻。自然电阻由两个细胞中紧密排列的缝隙连接通道的细胞质进入电阻组成。构建了一个数学模型来计算每个缝隙连接通道上的实际电压。该模型纳入了各个通道的随机开闭动力学。得出的结论是，即使在理想情况下完全补偿微电极串联电阻，缝隙连接中包含的通道数量也可能被大大低估。此外，归一化稳态连接电导可能被大大高估，从而容易掩盖跨连接电压依赖性。该模型用于讨论从双电压钳实验得出的结论，并为各种实验观察结果提供了替代解释。
