LOSS OF CFTR CHLORIDE CHANNELS ALTERS SALT ABSORPTION BY CYSTIC-FIBROSIS AIRWAY EPITHELIA IN-VITRO

Cystic fibrosis (CF) is caused by the loss of functional CFTR Cl- chan nels. However, it is not understood: how this defect disrupts salt and liquid movement in the airway or whether it alters the NaCl concentra tion in the thin liquid film covering the airway surface. Using a new approach, we found that CF airway surface liquid had a higher NaCl con centration than normal. Both CF and non-CF epithelia absorbed salt and liquid; however, expression of CFTR Cl- channels was required for max imal absorption. Thus, loss of CFTR Elevates the salt concentration in CF airway surface liquid and in sweat by related mechanisms; the elev ated NaCl concentration is due to a block in transcellular Cl- movemen t. The high NaCl may predispose CF airways to bacterial infections by inhibiting endogenous antibacterial defenses.