AIM: To explore the anti-fibrotic effect of Oxymatrine on CCU-induced liver fibrosis in rats and its modulation on the TGFbeta-Smad signaling pathway.METHODS: One hundred healthy male SD rats were randomly divided into three groups: normal group (/7 = 20), treatment group of Oxymatrine (n = 40) and CCU-induced fibrosis group {n = 40). Experimental hepatic fibrosis was induced by subcutaneous injection of carbon tetrachloride (CCU soluted in liquid paraffin with the concentration of 300 g/L, the dosage of injection was 3 mL/kg, twice per week for 8 wk). The treated rats received Oxymatrine via celiac injection at a dosage of 10 mg/kg twice a week at the same time. The deposition of collagen was observed with H&E and Masson staining. The concentration of serum TGF-pi was assayed with ELISA. The gene expression of Smads and CBP (CREB binding protein) was detected with in situ hybridization (ISH) and immunohistochemistry (IH), respectively. All the experimental figures were scanned and analyzed with special figure-analysis software.RESULTS: A significant reduction of collagen deposition and rearrangement of the parenchyma was noted in the liver tissue of Oxymatrine-treated rats. The semi-quantitative histological scores (2.43 ± 0.47 um2 vs 3.76 ± 0.68, P < 0.05) and average area of collagen in those rats were significantly decreased when compared with hepatic cirrhosis model rats (94.41 ± 37.26 urn2 vs 290.86 ± 89.37 um2, P < 0.05). The gene expression of Smad 3 mRNA was considerably decreased in the treated animals. The A value of Smad 3 mRNA was lower in the treated rats than the model rats (0.034 ± 0.090 us 0.167 ± 0.092, P < 0.05). Contrarily, the A value of Smad 7 mRNA was increased considerably in the treated animals (0.175 ± 0.065 vs 0.074 ± 0.012, P < 0.05). There was an obvious decrease in the expression of CBP mRNA in treated rats as illuminated by a reduction of its A value when compared with model rats (0.065 ± 0.049 us 0.235 ± 0.025, P < 0.001).CONCLUSION: Oxymatrine is effective in reducing the production and deposition of collagen in the liver tissue of experimental rats. Oxymatrine could promote the expression of Smad 7 and inhibit the expression of Smad 3 and CBP in CCU-induced hepatic fibrosis in SD rats, could modulate the fibrogenic signal transduction of TGFp-Smad pathway.