title: Sodium chloride regulation of the alpha epithelial amiloride-sensitive sodium channel (alphaENaC) gene requires syntheses of new protein(s).
abstract: The epithelial amiloride-sensitive sodium channel (ENaC) plays a central role in sodium homeostasis and blood pressure control. The molecular effect of high sodium intake on the ENaC gene is not well known. This study examined the effects of high salt (HS) intake on alphaENaC gene transcription in rat kidney. Rats were injected intraperitoneally with hypertonic (1.5M NaCl) or normal saline solution (three rats per group). The serum sodium concentration of rats injected with hypertonic saline increased significantly 30 min after injection (158 +/- 2 mM versus 140 +/- 1 mM for normal saline injected rats and 139 +/- 1 mM for uninjected rats). At 3 h after injection, serum sodium decreased (144 +/- 1 mM) but remained above the control values (139 +/- 1 mM for normal saline injected rats, 139 +/- 1 mM for uninjected rats). The serum aldosterone decreased 1.5 and 3 h after the hypertonic saline injection (217 +/- 10 and 139 +/- 23 pg/ml for hypertonic saline injected rats, 358 +/- 2 pg/ml for uninjected rats). The kidney cortex was dissected macroscopically and total RNA was isolated at 1.5 and 3 h after treatment. Semi-quantitative RT-PCR studies revealed that following hypertonic saline treatment, alphaENaC mRNA levels were dramatically downregulated, compared with controls, as early as 1.5h. Western blot analysis showed similar patterns of protein downregulation. Inhibition of protein synthesis by cycloheximide (CHX) blocked the sodium chloride-induced alphaENaC mRNA downregulation, 3h after treatment. This indicates that synthesis of new, uncharacterized protein(s) is required for sodium chloride-mediated inhibition of alphaENaC gene transcription.
authors.affiliation: Department of Bioscience and Biotechnology, College of Engineering, Institute of Biotechnology, Sejong University, Seoul, South Korea.
authors.forename: WonChung
authors.initials: W
authors.lastname: Lim
authors.forename: Dukkyung
authors.initials: D
authors.lastname: Kim
authors.forename: Jeong Bae
authors.initials: JB
authors.lastname: Park
authors.forename: Suhn Hee
authors.initials: SH
authors.lastname: Kim
authors.forename: YoungJoo
authors.initials: Y
authors.lastname: Lee
mesh_terms: D000818:Animals; D001483:Base Sequence; D003513:Cycloheximide / Q000494:pharmacology; D017931:DNA Primers; D053503:Epithelial Sodium Channels; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000235:genetics*; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D017931:DNA Primers; D053503:Epithelial Sodium Channels; D011500:Protein Synthesis Inhibitors; D015222:Sodium Channels; D012965:Sodium Chloride; D003513:Cycloheximide