Forty-five male C57BL/6 mice aged 8 to 10 weeks were randomly divided into sham operation group， liver fibrosis model group （model group） and calcitriol treatment group （treatment group）， with 15 mice in each group. The mice in sham operation group received the surgical line around the common bile duct without ligation； in model group， the common bile ducts of the mice were double-ligated and severed， and the mice in treatment group were injected intraperitoneally with calcitriol （2.5 μg·kg^－1） 3 times a week after operation. The mice in sham operation group and model group were injected with an equal volume of saline. The administration was continued until 4 weeks after the operation. On the 28th day， blood was taken from the orbit and the liver of the mouse was taken. On the second day after the operation， the activities of alanine aminotransferase （ALT） and aspartate aminotransferase （AST） and the levels of total bile acid （TBA）， total bilirubin （TBIL） and hydroxyproline （Hyp） in the serum of the mice in various groups were detected. The pathomorphology and fibrosis degrees of liver tissue were observed with hematoxylin and eosin （HE） and Sirius red staining. Western blotting method was used to detect the expression levels of vitamin D receptor（VDR），extracellular signal-regulated protein kinase （ERK），phosphorylated extracellular signal-regulated protein kinase （pERK）， α-smooth muscle protein （α-SMA），transforming growth factor-β1 （TGF-β1），type Ⅰ collagen （Col Ⅰ） and Desmin in liver tissue of the mice in various groups. Immunohistochemistry method was used to detect the expressions of α-SMA and TGF-β1 in liver tissue of the mice in various groups.

Compared with sham operation group， the serum activities of ALT and AST and the levels of TBA， TBIL and Hyp of the mice in model group were significantly increased （P<0.05）； compared with model group， the serum activities of ALT and AST and the levels of TBA， TBIL and Hyp in treatment group were significantly reduced （P<0.05）. The HE staining results showed that the liver lobules of the mice in sham operation group were normal， the tissue structure was relatively complete， and no inflammatory cell infiltration was seen； the liver tissue of the mice in model group had inflammatory cell infiltration， and necrosis and collagen deposition were more obvious； compared with model group， the necrotic area of ??liver tissue of the mice in treatment group was significantly reduced， and the inflammatory infiltration was improved. The Sirius red staining results showed that only a small amount of collagen deposition in liver tissue of the mice in sham operation group appeared around the central vein； the central vein and portal area of liver tissue of the mice in model group showed obvious collagen deposits； compared with model group， the collagen deposition in treatment group was significantly reduced. The Western blotting results showed that compared with sham operation group， the expression levels of ERK， p-ERK， α-SMA， TGF-β1， Col Ⅰ and Desmin in liver tissue of the mice in model group were significantly increased （P<0.05）； compared with model group， the expression levels of ERK， p-ERK， α-SMA， TGF-β1， Col Ⅰ and Desmin in liver tissue of the mice in treatment group were significantly reduced （P<0.05）. The immunohistochemical staining results showed that the expressions of α-SMA and TGF-β1 proteins in liver tissue of the mice in model group were higher than those in sham operation group， and the expressions of α-SMA and TGF-β1 proteins in treatment group were significantly lower than those in model group.

Calcitriol can reduce the activation of hepatic stellate cells （HSCs） by activating VDR， down-regulating the ERK protein expression， reducing the expression of TGF-β1，and inhibiting the deposition of collagen in tissue， thereby alleviate the BDL-induced liver fibrosis in the mice.