Enhanced expression of epithelial sodium channels in the renal medulla of Dahl S rats

Can J Physiol Pharmacol. 2011 Mar;89(3):159-68. doi: 10.1139/Y11-005.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Epithelial Sodium Channels / biosynthesis*
  • Epithelial Sodium Channels / genetics
  • Kidney Medulla / metabolism*
  • Kidney Medulla / pathology
  • Male
  • Protein Subunits / biosynthesis
  • Protein Subunits / genetics
  • Random Allocation
  • Rats
  • Rats, Inbred Dahl
  • Rats, Sprague-Dawley
  • Sodium, Dietary / administration & dosage*
  • Sodium, Dietary / adverse effects
  • Up-Regulation* / genetics

Substances

  • Epithelial Sodium Channels
  • Protein Subunits
  • Scnn1a protein, rat
  • Scnn1b protein, rat
  • Scnn1g protein, rat
  • Sodium, Dietary