Cyclic AMP-induced chloride permeability in the apical membrane of Necturus gallbladder epithelium.

作者：Karl‐Uwe Petersen, Luis Reuss · 发表于：The Journal of General Physiology · 年份：1983 · DOI：10.1085/jgp.81.5.705 · 被引用次数：124 · 研究领域：Ion Transport and Channel Regulation、Ion channel regulation and function、Neuroscience and Neuropharmacology Research

The effects of theophylline, 8-Br-cAMP, and cAMP on necturus gallbladder epithelium were investigated using microelectrode techniques. Each of these substances depolarized the cell membranes by approximately 15 mV and decreased the apparent ratio of apical to basolateral membrane resistances to a value not significantly different from zero. Examination of the ionic selectivity of the apical membrane by ion substitutions in the mucosal bathing medium revealed a large increase in Cl permeability with no apparent changes in K and Na permeabilities. Intracellular Cl activity ((a)CL(i)) was measured using Cl- sensitive liquid ion-exchanger microelectrodes. Under control conditions, (a)Cl(i) was approximately 20 mM, 2.5 times higher than the value expected for equilibrium distribution ((a)Cl(i/eq). After addition of 8-Br-cAMP, (a)Cl(i) decreased within less than 60 s to approximately 13 mM, a value not significantly different from ((a)Cl(i/eq)). Virtually identical results were obtained with theophylline. Under control conditions, luminal Cl removal caused (a)Cl(i) to fall at an initial rate of 1.8 mM/min, whereas in tissues exposed to 8-Br- cAMP or theophylline a rate of 11.6 mM/min was observed. The apical membrane Cl transference number was estimated from the change of (a)Cl(i) upon exposure to 8-Br-cAMP as well as from the changes in apical membrane potential during variation of the luminal Cl concentration. The results, 0.91 and 0.88, respectively, are indicative of a high Cl ...