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The amiloride-sensitive epithelial sodium channel (ENaC) is a heteromultimer of three homologous subunits (alpha-, beta-, and gamma- subunits). To study the role of the beta-subunit in vivo, we analyzed mice in which the betaENaC gene locus was disrupted. These mice showed low levels of betaENaC mRNA expression in kidney (approximately 1%), lung (approximately 1%), and colon (approximately 4%). In homozygous mutant betaENaC mice, no betaENaC protein could be detected with immunofluorescent staining. At birth, there was a small delay in lung- liquid clearance that paralleled diminished amiloride-sensitive Na+ absorption in tracheal explants. With normal salt intake, these mice showed a normal growth rate. However, in vivo, adult betaENaC m/m mice exhibited a significantly reduced ENaC activity in colon and elevated plasma aldosterone levels, suggesting hypovolemia and pseudohypoaldosteronism type 1. This phenotype was clinically silent, as betaENaC m/m mice showed no weight loss, normal plasma Na+ and K+ concentrations, normal blood pressure, and a compensated metabolic acidosis. On low-salt diets, betaENaC-mutant mice developed clinical symptoms of an acute pseudohypoaldosteronism type 1 (weight loss, hyperkalemia, and decreased blood pressure), indicating that betaENaC is required for Na+ conservation during salt deprivation.
Nikolaos Stergiopulos, Georgios Rovas, Sokratis Anagnostopoulos, Vasiliki Bikia, Patrick Segers
Nikolaos Stergiopulos, Stamatia Zoi Pagoulatou
Grégoire Courtine, Jocelyne Bloch, Jordan Squair, Léonie Asboth, Robin Jonathan Demesmaeker, Nicolas Hankov, Sergio Daniel Hernandez, Grégory Didier Dumont, Suje Amir, Maxime Berney