Experimental physiology
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Experimental physiology · Feb 2009
ReviewCongenital nephrogenic diabetes insipidus: what can we learn from mouse models?
Aquaporins (AQPs) are central players in mammalian physiology, allowing efficient water transport through cellular membranes. To date, 13 different aquaporins have been identified in mammals (AQP0-AQP12). Knocking out genes in mice and identification of mutations in the human genes provided important information on the role of AQPs in normal physiology. ⋯ In humans, mutations in the AQP2 gene cause congenital nephrogenic diabetes insipidus (NDI), a disorder characterized by an inability to concentrate urine in response to vasopressin. Until the recent development of several congenital NDI mouse models, our knowledge on AQP2 regulation was primarily based on in vitro studies. This review focuses on the similarities between the in vitro and in vivo studies and discusses new insights into congenital NDI obtained from the mouse models.
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Experimental physiology · Feb 2009
Role of the amiloride-sensitive epithelial Na+ channel in the pathogenesis and as a therapeutic target for cystic fibrosis lung disease.
Increased airway Na(+) absorption mediated by the amiloride-sensitive epithelial Na(+) channel (ENaC) is a basic defect in cystic fibrosis (CF) lung disease. Cystic fibrosis is one of the most common lethal hereditary diseases and is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The CFTR acts as a cAMP-dependent Cl(-) channel and regulator of ENaC, and CFTR dysfunction causes impaired Cl(-) secretion and increased Na(+) absorption in the airways of CF patients. ⋯ Studies of the pulmonary phenotype of betaENaC-overexpressing mice demonstrated that increased airway Na(+) absorption caused ASL depletion and reduced mucus transport, producing a CF-like lung disease with airway mucus plugging, chronic airway inflammation and pulmonary mortality. Further, recent pharmacological studies demonstrated that preventive, but not late, inhibition of increased airway Na(+) absorption with the ENaC blocker amiloride reduced morbidity and mortality in this murine model of CF lung disease. These results support a critical role of ENaC in the in vivo pathogenesis of CF lung disease and suggest that amiloride may be an effective preventive therapy for CF patients.