Dysfunction of the Epithelial Sodium Channel Expressed in the Kidney of a Mouse Model for Liddle Syndrome

Abstract

ABSTRACT. The Liddle syndrome is a dominant form of salt-sensitive hypertension resulting from mutations in the β or γ subunit of ENaC. A previous study established a mouse model carrying a premature Stop codon corresponding to the R566stopmutation (L) found in the original pedigree that recapitulates to a large extent the human disease. This study investigated the renal Na+transportin vivo,ex vivo(intact perfused tubules), andin vitro(primary cultured cortical collecting ducts [CCD]).In vivo, upon 6 to 12 h of salt repletion, after 1 week of low-salt diet, the L/L mice showed a delayed urinary sodium excretion, despite a lower aldosterone secretion as compared with controls. After 6 h salt of repletion, ENaC γ subunit is rapidly removed from the apical plasma membrane in wild-type mice, whereas it is retained at the apical membrane in L/L mice.Ex vivo, isolated perfused CCD from L/L mice exhibited higher transepithelial potential differences than perfused CCD isolated from +/+ mice.In vitro, confluent primary cultures of CCD microdissected from L/L kidneys grown on permeable filters exhibited significant lower transepithelial electrical resistance and higher negative potential differences than their cultured L/+ and +/+ CCD counterparts. The equivalent short-circuit current (Ieq) and the amiloride-sensitive Ieqwas approximately twofold higher in cultured L/L CCD than in +/+ CCD. Aldosterone (5 × 10−7M for 3 h) further increased Ieqfrom cultured L/L CCD. Thus, this study brings three independent lines of evidence for the constitutive hyperactivity of ENaC in CCD from mice harboring the Liddle mutation. e-mail: Bernard.Rossier@ipharm.unil.ch