Laboratory Animals >
Volume 42, Number 4 >
Pp. 389-412
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Figure 1 Transport in normal and cystic fibrosis (CF) airways. In a normal airway an appropriate balance between Na+ absorption (mediated by epithelial sodium channel [EnaC] in the apical membrane) and anion secretion (mediated by apical CF transmembrane conductance regulator [CFTR] and alternative anion channels) determines the volume of fluid on airway surfaces. This transport balance regulates the height of the periciliary liquid (PCL) in which cilia beat to permit effective mucus clearance. Mall et al. (2004) created a mouse overexpressing β-ENaC to augment sodium absorption. This reduced PCL depth impedes ciliary movement and mucus clearance whereas normally, CFTR downregulates ENaC activity. This process does not occur in CF because CFTR is absent or defective. In β-ENaC transgenic mice and perhaps in CF airways failure of mucus clearance promotes accumulation of airway secretory products, including glycosaminoglycans (GAGs) and pool of chemokines (e.g. interleukin-8), neutrophil proteases and growth factors that promote airway inflammation and mucus cell hyperplasia. Modified from Fizzell et al. (Frizzell & Pilewski 2004)
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