Background. Mucins are mucus glycoproteins that are kept compact inside mucous cells because their poly-anionic part are shielded by counter-ions. When mucus is secreted towards the airways, mucins expand to permit an efficient mucociliary clearance. This function, that requires rapid removal of cations, seems to depend on the presence of bicarbonate. In CF patients, the defective ion transport across mutated protein causes a simultaneous reduction of fluid, Cl^- and bicarbonate secretion leading to a viscous mucus phenotype with frequent infections and bacterial colonization of the airways.

Hypothesis and objectives. We have hypothesized, and aimed to demonstrate, that the consequence of the defective fluid and bicarbonate secretion in CF is an inappropriate structure of the mucus network with deficient rheological properties, and that pharmacological correction of the mutated CFTR may lead to recover the properties of mucus. In addition, we intended to determine whether inhalation of bicarbonate by CF patients can improve the properties of sputum.