title: The effect of varying tonicity on nasal epithelial ion transport in cystic fibrosis.
abstract: There is reasonable evidence that the fluid layer of the airway epithelium is exposed to changes in tonicity. The inspiration of cool, dry air causes an increased tonicity, whereas this tonicity may be decreased by glandular secretions. We hypothesized that the cystic fibrosis transmembrane conductance regulator (CFTR) is involved in the responses to changes in tonicity and that these may be altered in cystic fibrosis (CF). Using nasal potential difference (PD) protocols in 8 subjects with CF and 10 subjects without CF, we investigated the effects of hyper- and hypotonicity on ion transport processes. We found significant differences between the two groups. In response to a hypertonic challenge (mannitol 500 mM), there was a decreased PD in both groups, suggesting decreased sodium absorption. However, after the prior inhibition of sodium transport using amiloride, there was an increased PD in the non-CF group alone, suggesting CFTR-mediated chloride secretion in response to luminal hypertonicity. For the hypotonic solution, we found that hypotonicity inhibited CFTR-mediated chloride secretion in the non-CF group. These data suggest that CFTR plays a role in the recognition and regulation of airway fluid tonicity.
authors.affiliation: Department of Gene Therapy, Faculty of Medicine, Imperial College at the National Heart and Lung Institute, London SW3 6LR, UK.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Davies
authors.forename: Duncan M
authors.initials: DM
authors.lastname: Geddes
authors.forename: Eric W F W
authors.initials: EW
authors.lastname: Alton
mesh_terms: D000328:Adult; D000584:Amiloride / Q000494:pharmacology; D016022:Case-Control Studies; D046508:Culture Techniques; D003550:Cystic Fibrosis / Q000503:physiopathology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D004847:Epithelial Cells / Q000502:physiology; D005260:Female; D006801:Humans; D017136:Ion Transport / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials; D009297:Nasal Mucosa / Q000166:cytology / Q000187:drug effects*; D012016:Reference Values; D012494:Sampling Studies; D012680:Sensitivity and Specificity
chemical_list: C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000584:Amiloride; D007545:Isoproterenol