Altered NaCl concentration of airway surface liquid in cystic fibrosis.

A novel isotopic technique suggests that the [Na] and [Cl] of airway surface liquid are both normally approximately 50 mM. In cystic fibrosis, lack of the functional cystic fibrosis transmembrane conductance regulator (CFTR) causes failure of transcellular Cl absorption, resulting in an elevation of [Na] and [Cl] of airway surface liquid to approximately 100 mM.