Evidence that 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 d eciphering the ion channel after nystatin permeabilization of its basolater al or apical membrane (Hwang ct al., 1996). After apical membrane permeabil ization of rat primary cultured-airway monolayer, 4,4'-diisothiocyanatostil bene-2,2'-disulfonic acid (DIDS)-sensitive outwardly rectifying depolarizat ion-induced Cl- (BORDIC) currents were observed across the basolateral memb rane in symmetrical NMG-Cl solution in this study. No significant Cl- curre nt induced by the application of voltage clamping was observed across the a pical membrane in symmetrical NMG-Cl solution after basolateral membrane pe rmeabilization. The halide permeability sequence for BORDIC current was Br- is approximately equal to I- > Cl-. BORDIC current was not affected by bas olaterally applied bumetanide (0.5 mM). Basolateral DIDS (0.2 mM) but not a pical DIDS inhibited CFTR mediated short-circuit current (I-sc) in an intac t monolayer of rat airway epithelia, a T84 human colonal epithelial cell li ne, and a Calu-3 human airway epithelial cell line. This is the first ropor t showing that depolarization induced Cl- current is present on the basolat eral membrane of airway epithelia.