Long-term renal effects of unilateral ureteral obstruction and the role ofendothelin

Background. Angiotensin II (Ang II) and endothelin (ET) are involved in the alteration of renal function in unilateral ureteral obstruction (UUO). The renal response to Ang II following the reversal of a 24-hour UUO and the e ffect of ET blockade by bosentan during the time of obstruction were invest igated. Methods. Following blockade of the endogenous production of Ang II by capto pril, the renal response to Ang II was studied in rats 15 to 18 days after a 24-hour UUO (N = 10) or a sham operation (N = 9) both with (N = 10) and w ithout (N = 8) bosentan treatment in the periobstruction period. Similar st udies were performed in another group (N = 9) two months following the reve rsal of obstruction. Results. In the sham-operated group, Ang II reduced renal blood Row (RBF) b y 42 +/- 9% (P < 0.01), glomerular filtration rate (GFR) by 30 +/- 8% (P < 0.01), urine volume (UV) by 44 +/- 9% (P < 0.001), and absolute (UNaV) and fractional sodium excretion (FENa) by 52 +/- 9% (P < 0.001) and 33 +/- 9% ( P = 0.054), respectively. In the previously obstructed kidney, Ang II did n ot change RBF but increased GFR by 106 +/- 40% (P < 0.01), UV by 75 +/- 21% (P < 0.001), UNaV by 190 +/- 60% (P < 0.001), and FEN, by 40 +/- 13% (P < 0.05). Bosentan treatment in the obstructed group prevented these Ang II-in duced effects and did not have any effect on the sham-operated kidney. Two months following reversal of the obstruction, the response of the kidney wa s similar to that of the control kidney. Conclusion. Twenty-four-hour UUO results in a temporary abnormality in the renal response to Ang II, which is due, in part, to the actions of ET at th e time of obstruction.