In vivo microdialysis for determination of nasal liquid ion composition

Airway surface liquid (ASL) contains substances important in mucociliary clearance and airway defense. Little is known about substance concentrations in ASL because of its small volume and sampling difficulties. We used in vivo microdialysis (IVMD) to sample liquid lining the nasal cavity without net volume removal and incorporated into IVMD a potential difference (PD) electrode to assess airway integrity. The cystic fibrosis (CF) mouse nasal epithelia exhibit ion transport defects identical to those in CF human airways and, thus, are a good model for CF disease. We determined that nasal liquid [Na+] (107 ± 4 mM normal; 111 ± 9 mM CF) and [Cl−] (120 ± 6 mM normal; 122 ± 4 mM CF) did not differ between genotypes. The nasal liquid [K+] (8.7 ± 0.4 mM) was significantly less in normal than in CF mice (16.6 ± 4 mM). IVMD accurately samples nasal liquid for ionic composition. The ionic composition of nasal liquid in the normal and CF mice is similar.