WHOLE-CELL CHLORIDE CONDUCTANCES IN CULTURED BRUSHED HUMAN NASAL EPITHELIAL-CELLS

Human airway epithelial cells were obtained by nasal brushing, thus avoiding the use of proteolytic enzymes for cell isolation. Whole-cell Cl- conductances were studied in these cells by means of the patch-clamp technique. During whole-cell recordings, cell swelling activated a Cl conductance that was blocked by indanyloxyacetic acid (48 +/- 10% inhibition at 50 muM). The swelling-induced current outwardly rectified and showed inactivation at depolarizing voltages (greater-than-or-equal-to +60 mV) and activation at hyperpolarizing voltages (less-than-or-equal-to -30 mV). The voltage sensitivity of current activation was approximately twice that of inactivation. Another Cl- current with different kinetics was observed when nonswollen airway cells were stimulated with ionomycin (2 muM) in the presence of 1 mM Ca2+. The Ca2+-induced current exhibited activation during depolarizing voltage steps (greater-than-or-equal-to +40 mV) and inactivation during hyper-polarizing voltage steps (less-than-or-equal-to -40 mV). In contrast to the swelling-induced current, the activation of Ca2+-induced current was less sensitive to voltage compared with its inactivation. Tail current analysis suggested that Cl- channels having a linear current-voltage relation mediate the response to Ca2+. This study indicates that brushed human nasal epithelial cells possess Cl- conductances that are regulated by cell swelling and Ca2+ and that they represent a useful in vitro model for studying ion transport in epithelia.