Journal
AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY
Volume 285, Issue 5, Pages F889-F901Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajprenal.00170.2003
Keywords
proximal tubule; thick ascending limb of Henle's loop; distal convoluted tubule; collecting duct; Na-Cl cotransporters; sodium excretion
Categories
Funding
- NATIONAL HEART, LUNG, AND BLOOD INSTITUTE [Z01HL001285] Funding Source: NIH RePORTER
- Intramural NIH HHS [Z99 HL999999, Z01 HL001285-21] Funding Source: Medline
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Urinary tract obstruction impairs urinary concentrating capacity and reabsorption of sodium. To clarify the molecular mechanisms of these defects, expression levels of renal sodium transporters were examined in rats with 24-h bilateral ureteral obstruction (BUO) or at day 3 or 14 after release of BUO (BUO-R). BUO resulted in downregulation of type 3 Na+/H+ exchanger (NHE3) to 41+/-14%, type 2 Na-Pi cotransporter (NaPi-2) to 26+/-6%, Na-K-ATPase to 67+/-8%, type 1 bumetanide-sensitive Na-K-2Cl cotransporter (BSC-1) to 20+/-7%, and thiazide-sensitive cotransporter (TSC) to 37+/-9%. Immunocytochemistry confirmed downregulation of NHE3, NaPi-2, Na-K-ATPase, BSC-1, and TSC. Consistent with this downregulation, BUO-R was associated with polyuria, reduced urinary osmolality, and increased urinary sodium and phosphate excretion. BUO-R for 3 days caused a persistant downregulation of NHE3 to 53+/-10%, NaPi-2 to 57+/-9%, Na-K-ATPase to 62+/-8%, BSC-1 to 50+/-12%, and TSC to 56+/-16%, which was associated with a marked reduction in the net renal reabsorption of sodium (616+/-54 vs. 944+/-24 mumol.min(-1).kg(-1); P<0.05) and phosphate (6.3 +/- 0.9 vs. 13.1 +/- 0.4 mu mol.min(-1).kg(-1); P<0.05) demonstrating a defect in renal sodium and phosphate reabsorption capacity. Moreover, downregulation of Na-K-ATPase and TSC persisted in BUO-R for 14 days, whereas NHE3, NaPi-2, and BSC-1 were normalized to control levels. In conclusion, downregulation of renal Na transporters in rats with BUO and release of BUO are likely to contribute to the associated urinary concentrating defect, increased urinary sodium excretion, and postobstructive polyuria.
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