Electrophysiology of plasma membrane vesicles.
Electrophysiology of plasma membrane vesicles.
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质膜囊泡的电生理学。
DOI：
10.1152/ajprenal.1984.246.4.f363
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Wright,EM
中科院分区：
文献类型：
--
作者：
Wright,EM
在肾脏和胃肠道生理学中，使用从顶端和基底外侧细胞膜分离的囊泡来研究上皮运输现象已变得流行。囊泡制剂中的转运通常用放射性示踪剂进行监测，但最近的注意力已转向电生理学方法。由于不可能用经典的电生理技术测量小囊泡（直径小于 500 nm）中膜的电特性，因此必须采用间接方法。在这篇综述中，我重点关注电压敏感光学探针在测量刷状缘膜囊泡中膜电位的应用。在存在离子载体的情况下，使用已知离子梯度产生的扩散电势来校准光信号，例如，在存在缬氨霉素的情况下使用 K 梯度进行 EKS。膜电位测量可用于 1) 说明刷状缘膜中糖、氨基酸和羧酸-Na 共转运系统的特异性和动力学，2) 确定刷状缘膜的离子渗透性。所有已知通过 Na 共转运跨刷状缘膜的有机溶质都会以 Na 依赖性、可饱和的方式使膜去极化。结果在定性和定量上都与在完整肾小管中获得的电生理学数据以及囊泡中示踪剂的摄取一致。双离子电位测量表明刷状缘膜对阴离子和阳离子具有选择性渗透性，但有迹象表明渗透性在某种程度上取决于囊泡制备方法和实验条件。然而，电位测量可以深入了解囊泡制剂中离子传输的机制，并且膜片钳技术的应用应该在未来提供进一步的收益。
In both renal and gastrointestinal physiology, it has become popular to study epithelial transport phenomena using vesicles isolated from the apical and basolateral cell membranes. Transport in vesicle preparations is usually monitored with radioactive tracers, but more recently attention has been directed to electrophysiological methods. As it is impossible to measure the electrical properties of membranes in small vesicles (less than 500 nm diam) with classical electrophysiological techniques, indirect methods have to be employed. In this review I focus on the application of voltage-sensitive optical probes to measure membrane potentials in brush border membrane vesicles. Optical signals are calibrated with diffusion potentials generated with known ion gradients in the presence of ionophores, e.g., EKS with K gradients in the presence of valinomycin. Membrane potential measurements can be used 1) to illustrate the specificity and kinetics of sugar-, amino acid-, and carboxylic acid-Na cotransport systems in brush border membranes, and 2) to determine the ion permeability of brush border membranes. All organic solutes known to be transported by Na cotransport across brush border membranes depolarize the membrane in a Na-dependent, saturable manner. The results agree, both qualitatively and quantitatively, with electrophysiological data obtained in the intact renal tubule and with tracer uptake in vesicles. Bi-ionic potential measurements demonstrate that brush border membranes are permselective to anions and cations, but there are indications that the permeabilities are somewhat dependent on the method of vesicle preparation and the experimental conditions. However, electrical potential measurements provide insight into the mechanisms of ion transport in vesicle preparations, and the application of patch-clamp techniques should provide further gains in the future.