Altered expression of urea transporters in response to ureteral obstruction.

Abstract

Urea plays an important role in the urinary concentrating capacity. Renal inner medullary (IM) urea transporter expression was examined in rats with bilateral (BUO) or unilateral ureteral obstruction (UUO). BUO (24 h) was associated with markedly increased plasma urea (42.4 +/- 1.0 vs. 5.2 +/- 0.2 mmol/l) and a significant decrease in expression of UT-A1 (28 +/- 8% of sham levels), UT-A3 (45 +/- 11%), and UT-B (70 +/- 8%). Immunocytochemistry confirmed downregulation of UT-A1 and UT-A3 in IM collecting duct and UT-B in the descending vasa recta. Three days after release of BUO, UT-A1, UT-A3, and UT-B remained significantly downregulated (UT-A1: 37 +/- 6%; UT-A3: 25 +/- 6%; and UT-B: 10 +/- 5% of sham levels; P < 0.05) concurrent with a persistent polyuria and a marked reduction in solute-free water reabsorption (115 +/- 11 vs. 196 +/- 8 microl.min(-1).kg(-1), P < 0.05). Moreover, 14 days after release of BUO, total UT-A1, UT-A3, and UT-B remained significantly decreased compared with sham-operated controls and urine urea remained reduced (588 +/- 43 vs. 1,150 +/- 94 mmol/l). Consistent with increased levels of plasma urea 24 h after onset of UUO (7.4 +/- 0.3 vs. 4.8 +/- 0.3 mmol/l), the protein abundance of UT-A1, UT-A3, and UT-B in IM was markedly reduced in the obstructed kidney, which was confirmed by immunocytochemistry. In the nonobstructed kidney, the expression of urea transporters did not change. In conclusion, reduced expression of UT-A1, UT-A3, and UT-B levels in both BUO and UUO rats suggests that urea transporters play important roles in the impaired urinary concentrating capacity in response to urinary tract obstruction.

• Authors: Chunling Li, Janet D Klein, Weidong Wang, Mark A Knepper, Søren Nielsen, Jeff M Sands, Jørgen Frøkiaer
• Journal: American journal of physiology. Renal physiology (Am J Physiol Renal Physiol) Vol. 286 Issue 6 Pg. F1154-62 (Jun 2004) ISSN: 1931-857X [Print] United States
• PMID: 14982816 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Membrane Transport Proteins
• urea transporter

Topics

• Animals
• Blotting, Western
• Densitometry
• Down-Regulation (physiology)
• Electrophoresis, Polyacrylamide Gel
• Gene Expression Regulation (physiology)
• Immunohistochemistry
• Kidney Medulla (metabolism)
• Male
• Membrane Transport Proteins (biosynthesis)
• Rats
• Rats, Wistar
• Ureteral Obstruction (metabolism)