Objective   To investigate the effect of fosinopril on the expression of transforming growth factor (TGF)-activated kinase 1 (TAK-1) in the kidney of rats with unilateral ureteral obstruction (UUO)

and its protective effect on renal interstitial fibrosis (RIF).    Methods   UUO model was induced by ligating the left ureter in rats. A total of 72 male Sprague-Wistar rats were randomly divided into 3 groups: sham-operated group (n=24)

UUO model group (n=24) and UUO+fosinopril group (n=24). The rats were treated with 10 mg/(kg·d) by gastric gavage in the fosinopril treated group from 2 d after the operation

and the rats were treated with the identical dose of normal saline in the other 2 groups. Eight rats of each group were sacrificed at 7

14 and 21 d after UUO. Pathological changes of the renal tissue were observed by HE and Masson staining

and the mRNA and protein expression of TAK1 was detected by in situ hybridization

real-time PCR and Western blot analysis.    Results   The renal interstitial damage index of UUO group was increased compared with that of the sham-operation group (P0.05)

but was decreased in fosinopril treatment group (P0.05). The protein expression of TAK1 and its mRNA in UUO group were up-regulated compared with those in the sham-operation group (P0.05)

but decreased in fosinopril treatment group at the same time points (P0.05).    Conclusion   Fosinopril may play a protective role in the kidney and alleviate RIF after UUO by down-regulating the expression of TAK1.