Pusch M, Neher E
Max-Planck-Institut für biophysikalische Chemie, Göttingen, Federal Republic of Germany.
Pflugers Arch. 1988 Feb;411(2):204-11. doi: 10.1007/BF00582316.
(1) Fluorescent compounds and specific ion currents (Na+, K+) were used to study the kinetics of the diffusional exchange between small cells and patch pipettes in the tight seal whole cell configuration of the patch clamp technique. (2) Changes in the intracellular concentration of the test substances following patch rupture could be fitted with single exponentials, provided the access resistance RA of the pipette remained constant during diffusional equilibration. The diffusion time constants were linearly related to the access resistance. (3) When apparent diffusion rates were normalized with respect to access resistance they were found to be dependent on the cell size. However, the cell capacitance, which is proportional to the membrane area turned out not to be a precise measure of the cell size. (4) The experimental diffusion rates changed systematically with the aqueous diffusion coefficient and the inverse third root of the molecular weight. Linear interpolation with respect to these quantities provided estimates of diffusion time constants for the diffusion between patch pipettes and the cytoplasm for substances of interest.
(1) 利用荧光化合物和特定离子电流（Na⁺、K⁺），在膜片钳技术的紧密封全细胞配置下，研究小细胞与膜片吸管之间扩散交换的动力学。(2) 只要在扩散平衡期间吸管的接入电阻RA保持恒定，膜片破裂后测试物质细胞内浓度的变化就可以用单指数函数拟合。扩散时间常数与接入电阻呈线性相关。(3) 当表观扩散速率相对于接入电阻进行归一化时，发现它们取决于细胞大小。然而，与膜面积成正比的细胞电容并非细胞大小的精确度量。(4) 实验扩散速率随水扩散系数和分子量的倒数立方根而系统地变化。对这些量进行线性插值，可估算出感兴趣物质在膜片吸管与细胞质之间扩散的扩散时间常数。
