WHOLE-CELL CL- CURRENTS IN A HUMAN PERIPHERAL AIRWAY EPITHELIAL-CELL LINE

We have used the whole-cell patch-clamp technique to identify and char acterize Cl- currents in a cell line derived from human peripheral air way epithelium (NCI-H-441-4). The permeability sequence and relative s electivity for different anions was Br-(1.4) similar to I-(1.3) > Cl-( 1.0) > F-(0.6) > gluconate (0.4) > glutamate (0.2). The current-voltag e relationship displayed rectification in the outward direction. Diphe nylamine-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 blo cked by extracellularly applied 5-nitro-2-(3-phenylpropylamino)benzoat e (NPPB), with an estimated IC50 of 15.2 mu M. Dibutyryl-cyclic AMP (1 0(-4) M) increased outward current, whereas pretreatment with 100 ng/m L pertussis toxin almost completely abolished the Cl- current. Pertuss is toxin inhibition of this current could be partially reversed by dia lysis of the cell interior with the activated alpha(i-2), subunit of G (i) protein. This cell line provides an opportunity to study directly the regulation of Cl- channels in cells derived from the peripheral hu man lung airways.