Stimulation by in vivo and in vitro metabolic acidosis of expression of rBSC-1, the Na+-K+(NH4+)-2Cl- cotransporter of the rat medullary thick ascending limb.
To assess whether metabolic acidosis per se regulates rBSC-1, the rat medullary thick ascending limb (MTAL) apical Na+-K+(NH4+)-2Cl- cotransporter, rat MTALs were incubated for 16 h in an acid 1:1 mixture of Ham's nutrient mixture F-12 and Dulbecco's modified Eagle's medium. Cotransport activity was estimated in intact cells and membrane vesicles by intracellular pH and 22Na+ uptake measurements, respectively; rBSC-1 protein was quantified by immunoblotting analysis and mRNA by quantitative reverse transcription-polymerase chain reaction. As compared with incubation at pH approximately 7.35, acid incubation (pH approximately 7.10) up-regulated by 35-100% rBSC-1 transport activity in cells and membrane vesicles, and rBSC-1 protein and mRNA abundance. In contrast, acid incubation did not alter alkaline phosphatase and Na+/K+-ATPase enzyme activities or beta-actin protein abundance. After 3 h of in vivo chronic metabolic acidosis (CMA) rBSC-1 mRNA abundance increased in freshly harvested MTALs, which was accompanied after 1-6 days of CMA with enhanced rBSC-1 protein abundance. These results demonstrate that both in vivo and in vitro CMA stimulate rBSC-1 expression, which would contribute to the adaptive increase in MTAL absorption and urinary excretion of NH4+ in response to CMA.
Attmane-Elakeb
A
A
INSERM Unité 356, Physiologie et Endocrinologie Cellulaire et Moléculaire Rénale, Université Pierre et Marie Curie, 75006 Paris, France.
Mount
D B
DB
Sibella
V
V
Vernimmen
C
C
Hebert
S C
SC
Bichara
M
M
D000138:Acidosis / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers; D005786:Gene Expression Regulation; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D007679:Kidney Medulla / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D028021:Sodium-Potassium-Chloride Symporters
D002352:Carrier Proteins; D017931:DNA Primers; D012333:RNA, Messenger; D028021:Sodium-Potassium-Chloride Symporters