Objective:To assess the formular Buyang Huanwu decoction on α-smooth muscle actin（α-SMA） in renal tubulointerstitial fibrosis rats caused by unilateral ureteral obstruction.Method: The renal tubulointerstitial fibrosis model was caused by unilateral ureteral obstruction（UUO） in SD rats.The rats were divided into four groups

namely

sham operation group

modeling group

enalapril treated group and Buyang Huanwu decoction treated group.Rats were sacrificed at 7

14

28 d during experiment period for examination of renal function using light microscopy

hematoxylin-eosin staining

Masson staining for the evaluation of interstitium injury index and immunohistochemistry for α-SMA.Result: The renal function of modeling rats declined compared with sham-group rats.The renal function of rats received either enalapril or Buyang Huanwu decoction significantly improved compared modeling rats.Light microscopy showed that the rats undertook UUO had significant tubulointerstitial fibrosis and both enalapril and sig Buyang Huanwu decoction nificantly improved the renal lesions.At each time point

the interstitium injury index and expression of α-SMA in modeling rats were significantly increased compared with rats received sham operation.Enalapril and Buyang Huanwu decoction significantly decreased the interstitium injury index and expression of α-SMA at d 7（P<0.05）;the index and expression of α-SMA was further decreased in the next three weeks with extreme significance（P<0.01）.Conclusion: The formular Buyang Huanwu decoction can improve renal function and morphology destruction

decrease the interstitium injury index and expression of α-SMA in renal fibrosis rats caused by UUO.The results indicate the formular Buyang Huanwu decoction may have beneficial effects on tubulointerstitial fibrosis.