title: Enhanced expression of epithelial sodium channels in the renal medulla of Dahl S rats.
abstract: Inner medullary collecting duct (IMCD) cells from salt-sensitive (S) Dahl rats transport twice as much Na(+) as cells from salt-resistant (R) rats, possibly related to dysregulation of the renal epithelial sodium channel (ENaC). The effect of a high-salt diet on ENaC expression in the inner medulla of S versus R rats has not yet been studied. Young, male S and R rats were placed on a regular-salt (0.3%) or high-salt (8%) diet for 2 or 4 weeks. mRNA and protein expression of ENaC subunits were studied by real-time PCR and immunoblotting. Intracellular distribution of the subunits in the IMCD was evaluated by immunohistochemistry. On regular salt, the abundance of the mRNA of β and γENaC was higher in the medulla of S rats than R rats. This was associated with a greater protein abundance of 90 kDa γENaC and higher immunoreactivity for both α and γ ENaC. High salt did not affect mRNA abundance in either strain and decreased apical staining of βENaC in IMCD of R rats. In contrast, high salt did not affect the higher apical localization of αENaC and increased the apical membrane staining for β and γENaC in the IMCD of S rats. Expression of ENaC subunits is enhanced in the medulla of S vs. R rats on regular salt, and further increased on high salt. The persistent high expression of αENaC and increase in apical localization of β and γENaC may contribute to greater retention of sodium in S rats on a high-salt diet.
authors.affiliation: Hypertension Unit, University of Ottawa Heart Institute, ON, Canada.
authors.forename: Md Shahrier
authors.initials: MS
authors.lastname: Amin
authors.forename: Erona
authors.initials: E
authors.lastname: Reza
authors.forename: Esraa
authors.initials: E
authors.lastname: El-Shahat
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Frédérique
authors.initials: F
authors.lastname: Tesson
authors.forename: Frans H H
authors.initials: FH
authors.lastname: Leenen
mesh_terms: D000818:Animals; D053503:Epithelial Sodium Channels / Q000096:biosynthesis* / Q000235:genetics; D007679:Kidney Medulla / Q000378:metabolism* / Q000473:pathology; D008297:Male; D021122:Protein Subunits / Q000096:biosynthesis / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D020303:Rats, Inbred Dahl; D017207:Rats, Sprague-Dawley; D012982:Sodium, Dietary / Q000008:administration & dosage* / Q000009:adverse effects; D015854:Up-Regulation / Q000235:genetics
chemical_list: D053503:Epithelial Sodium Channels; D021122:Protein Subunits; C440894:Scnn1a protein, rat; C507050:Scnn1b protein, rat; C507054:Scnn1g protein, rat; D012982:Sodium, Dietary