Salutary role for angiotensin in partial urinary tract obstruction

Background. In the neonatal period, angiotensin II (Ang II) is up-regulated and induces a timely development of the renal pelvis and ureteral peristal sis, thereby protecting the kidney from hydronephrosis. We tested the possi bility that in adulthood, Ang II may act salutarily on the kidney structure during partial urinary tract obstruction by inducing adaptive changes in t he peristaltic machinery. Methods. Adult male Sprague-Dawley rats were subjected to partial unilatera l ureteral obstruction (UUO) and divided into two groups, that is, those tr eated with (group L, N = 21) and those without (group C, N = 21) an angiote nsin type 1 (AT1) receptor antagonist (losartan). Control animals were sham operated (N = 10). Rats were sacrificed either at day 7 or day 14. Results. The degree of hydronephrosis determined morphometrically was signi ficantly more severe in group L than group C at both day 7 and day 14, indi cating that Ang II inhibition accentuated hydronephrosis. The measurement o f upstream pressure within the partially ligated ureter in vivo revealed th at losartan significantly attenuates the frequency of ureteral peristaltic activities. In in vitro studies using ureteral strips harvested from normal adult Sprague-Dawley rats (N = 10), Ang II (10(-8) mol/L) was shown to aug ment contraction, which was completely inhibited by losartan (10(-6) mol/L) . Conclusions. Ang II has a salutary effect of protecting kidneys from hydron ephrosis during partial ureteral obstruction through its ability to augment ureteral peristalsis.