title: Acid pH increases the stability of BSC1/NKCC2 mRNA in the medullary thick ascending limb.
abstract: Chronic metabolic acidosis enhances the ability of the medullary thick ascending limb (MTAL) to absorb NH(4)(+) at least in part by stimulating the mRNA and protein expression of BSC1/NKCC2, the MTAL apical Na(+)-K(+)(NH(4)(+))-2Cl(-) co-transporter. For assessing the mechanism by which an acid pH enhances the BSC1 mRNA abundance, MTAL were harvested from adrenalectomized rats and incubated in control (pH 7.35) and acid (pH 7.10) 1:1 mixtures of Ham's nutrient mixture F-12 and DME. rBSC1 mRNA abundance and gene transcription rate were quantified by quantitative reverse transcription-PCR and run-off assay, respectively. Acid incubation enhanced mRNA abundance within 4 h in whole cell (P < 0.02) but not in nucleus. BSC1 gene transcription rate was not affected by acid incubation. In contrast, under conditions in which gene transcription was blocked, rBSC1 mRNA decreased within 6 h by 38 +/- 11% in control but only by 15 +/- 15% in acid medium (P < 0.02), which represented an increase in the BSC1 mRNA half-life from approximately 7 to approximately 17 h. Furthermore, in a mouse TAL cell line, acid incubation for 16 h significantly increased (P < 0.02) the amount of BSC1 mRNA in cells transfected with the full-length mBSC1 cDNA but not in cells transfected with a mBSC1 cDNA lacking the 3'-UTR. These results demonstrate that acid pH enhances the stability of BSC1 mRNA probably by activating pathways that act on the AU-rich 3'-UTR of BSC1 mRNA, which contributes to the renal response to metabolic acidosis.
authors.affiliation: INSERM U.426, Institut Fédératif Régional Claude Bernard, Faculté de Médecine Xavier Bichat, Université Paris 7, Paris, France.
authors.forename: Zoubida
authors.initials: Z
authors.lastname: Karim
authors.forename: Amel
authors.initials: A
authors.lastname: Attmane-Elakeb
authors.forename: Valérie
authors.initials: V
authors.lastname: Sibella
authors.forename: Maurice
authors.initials: M
authors.lastname: Bichara
mesh_terms: D000138:Acidosis / Q000235:genetics / Q000503:physiopathology*; D000818:Animals; D002478:Cells, Cultured; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007679:Kidney Medulla / Q000503:physiopathology*; D007684:Kidney Tubules / Q000503:physiopathology; D051379:Mice; D020871:RNA Stability / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics*; D064466:Solute Carrier Family 12, Member 1; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D012333:RNA, Messenger; C578715:Slc12a1 protein, mouse; C578716:Slc12a1 protein, rat; D028021:Sodium-Potassium-Chloride Symporters; D064466:Solute Carrier Family 12, Member 1