Evidence for basolateral but not apical membrane localization of outwardly rectifying depolarization-induced Cl(-) channel in airway epithelia.

The rat primary cultured-airway monolayer had been an excellent model for deciphering the ion channel after nystatin permeabilization of its basolateral or apical membrane (Hwang et al., 1996). After apical membrane permeabilization of rat primary cultured-airway monolayer, 4,4'-diisothiocyanatostilbene-2, 2'-disulfonic acid (DIDS)-sensitive outwardly rectifying depolarization-induced Cl(-) (BORDIC) currents were observed across the basolateral membrane in symmetrical NMG-Cl solution in this study. No significant Cl(-) current induced by the application of voltage clamping was observed across the apical membrane in symmetrical NMG-Cl solution after basolateral membrane permeabilization. The halide permeability sequence for BORDIC current was Br(-) = I(-) > Cl(-). BORDIC current was not affected by basolaterally applied bumetanide (0.5 mm). Basolateral DIDS (0.2 mm) but not apical DIDS inhibited CFTR mediated short-circuit current (I(sc)) in an intact monolayer of rat airway epithelia, a T84 human colonal epithelial cell line, and a Calu-3 human airway epithelial cell line. This is the first report showing that depolarization induced Cl(-) current is present on the basolateral membrane of airway epithelia.