Whole-cell Cl- currents in a human peripheral airway epithelial cell line

We have used the whole-cell patch-clamp technique to identify and characterize Cl- currents in a cell line derived from human peripheral airway epithelium (NCI-H-441-4). The permeability sequence and relative selectivity for different anions was Br- (1.4) approximately I- (1.3) > Cl- (1.0) > F- (0.6) > gluconate (0.4) > glutamate (0.2). The current-voltage relationship displayed rectification in the outward direction. Diphenylamine-2-carboxylate (10(-4) M) applied intracellularly blocked the outward-rectified current, while extracellularly applied diphenylamine-2-carboxylate had no effect on Cl- current. This current was also blocked by extracellularly applied 5-nitro-2-(3-phenylpropylamino)benzoate (NPPB), with an estimated IC50 of 15.2 microM. Dibutyryl-cyclic AMP (10(-4) M) increased outward current, whereas pretreatment with 100 ng/mL pertussis toxin almost completely abolished the Cl- current. Pertussis toxin inhibition of this current could be partially reversed by dialysis of the cell interior with the activated alpha i-2 subunit of Gi protein. This cell line provides an opportunity to study directly the regulation of Cl- channels in cells derived from the peripheral human lung airways.