Narvarte J, Finn A L
J Gen Physiol. 1980 Jul;76(1):69-81. doi: 10.1085/jgp.76.1.69.
Membrane potentials and the electrical resistance of the cell membranes and the shunt pathway of toad urinary bladder epithelium were measured using microelectrode techniques. These measurements were used to compute the equivalent electromotive forces (EMF) at both cell borders before and after reductions in mucosal Cl- concentration ([Cl]m). The effects of reduction in [Cl]m depended on the anionic substitute. Gluconate or sulfate substitutions increased transepithelial resistance, depolarized membrane potentials and EMF at both cell borders, and decreased cell conductance. Iodide substitutions had opposite effects. Gluconate or sulfate substitutions decreased apical Na conductance, where iodide replacements increased it. When gluconate or sulfate substitutions were brought about the presence of amiloride in the mucosal solution, apical membrane potential and EMF hyperpolarized with no significant changes in basolateral membrane potential or EMF. It is concluded that: (a) apical Na conductance depends, in part, on the anionic composition of the mucosal solution, (b) there is a Cl- conductance in the apical membrane, and (c) the electrical communication between apical and basolateral membranes previously described is mediated by changes in the size of the cell Na pool, most likely by a change in sodium activity.
使用微电极技术测量了蟾蜍膀胱上皮细胞膜电位、细胞膜电阻和分流途径。这些测量结果用于计算黏膜 Cl⁻ 浓度（[Cl]m）降低前后细胞两侧的等效电动势（EMF）。[Cl]m 降低的影响取决于阴离子替代物。葡萄糖酸盐或硫酸盐替代增加了跨上皮电阻，使细胞两侧的膜电位和 EMF 去极化，并降低了细胞电导。碘化物替代则产生相反的效果。葡萄糖酸盐或硫酸盐替代降低了顶端 Na⁺ 电导，而碘化物替代则增加了顶端 Na⁺ 电导。当在黏膜溶液中存在氨氯吡咪的情况下进行葡萄糖酸盐或硫酸盐替代时，顶端膜电位和 EMF 超极化，而基底外侧膜电位或 EMF 无显著变化。得出以下结论：（a）顶端 Na⁺ 电导部分取决于黏膜溶液的阴离子组成，（b）顶端膜存在 Cl⁻ 电导，（c）先前描述的顶端和基底外侧膜之间的电通讯是由细胞 Na⁺ 池大小的变化介导的，很可能是由钠活性的变化介导的。
