Abstract: Objective To observe the changes of calpain 2,caspase-3 expression in liver fibrosis and to explore their effects on liver fibrosis in rats.Methods Forty male Wistar rats were randomly divided into four groups (4 weeks normal control group,8 weeks normal control group,4 weeks liver fibrosis model group and 8 weeks liver fibrosis model group,10 in each group).The model groups were treated with hypodermic injection of 40% carbon tetrachloride (CCl₄)every 3 day for 4 weeks and 8 weeks,respectively,at the dosage of 0.3 ml/100 g body weight.The liver index,blood alanine aminotransfersase (ALT)and aspartate amiontransferase (AST)were analyzed.The liver fibrosis was observed with microscope.Additionally,the expression of calpain 2 and activated caspase-3 protein were determined by immunohistochemistry and western blot;mRNA expression of calpain 2 was determined with real-time PCR.Results The level of ALT and AST in 4 weeks model group (727.00±249.70 and 1 260.00±579.25 U/L) and in 8 weeks model group (616.00±209.98 and 1167.00±318.18 U/L)were obviously higher than those of normal control groups(P<0.01).The protein(23.1±3.77)and mRNA(167.93±50.39)expression of calpain 2 in liver tissue of 8 weeks fibrosis model group were obviously higher than those in normal age-matched control group(P<0.01).Compared with the control groups,the protein of activated caspase-3 (18.76±3.54 and 25.46±4.77)in 4 weeks and 8 weeks liver fibrosis model group also elevated(P<0.01).Conclusion In the process of liver fibrosis induced by CCl₄,the expression of calpain 2 and caspase-3 increase obviously,suggesting that calpain 2 and caspase-3 may play important roles in liver fibrosis.