Abstract: Objective To study the effect of all-transretinoic acid(at-RA) on the process of renal interstitial fibrosis following unilateral ureteral obstruction (UUO) in rats. Methods Fouty SD rats were randomly assigned into 5 groups: Two atRA treatment groups (10mg and 20mg·kg-1·d-1 respectively), benazepril treatment group(10mg·kg-1·d-1), UUO control group and normal control group. All of rats were killed 14 days after surgery. Immunohistochemistry was performed on renal tissue to detect smooth muscle actin(α-SMA) which was a cytoskeletal marker of myofibroblast (MyoF) and collagen Ⅲ(col Ⅲ). Histological studies were also done by he and MASSON stainting. Results　Fourteen days after surgery, interstitial myof infiltration and interstitial colⅢdeposition were all significantly reduced by at-RA treatment. At-RA treatment also improved the histological changes of UUO rats. Conclusion Reduction of interstitial MyoF infiltration may be an important event by which at-RA prevents renal injury caused by UUO.

Key words: α-smooth muscle actin, All-transretinoic acid, Collagen Ⅲ, Ureteral obstruction, Myofibroblast