In the present study, we showed that UUO rats displayed renal interstitial injury and fibrosis after 14 days of surgery, characterized by relatively increasing levels in serum creatinine, elevated tubulointerstitial injury index and score of tubulointerstitial fibrosis, and high expression of Col I mRNA/protein and α-SMA in obstructive renal tissues. This evidence concerns the gene ACTA1 and fibrosis.