Aim To study the effect of alendronate on the expression of osteoprotegerin(OPG) in rat aorta,and investigate the possible mechanism of inhibiting artery calcification by alendronate. Methods Eighteen 4-week-old male SD rats were randomly divided into the control group(n=6),calcification group(n=6) and alendronate group(n=6).The later two groups were subcutaneously injected with warfarin(150 mg/kg per 12 hours for 5 days) and Vitamin D3[3 MU/(kg·d) for 3 days] to induce extensive calcification of the aorta.Alendronate group was treated with daily subcutaneous injection of alendronate 4 days before the first warfarin dose.The control group was given daily subcutaneous injection of 0.9%NaCl.Thoracic aortas were exercised for analysis of calcification and OPG expression using histomorphometry,spectrophotome RT-PCR and immunohistochemistry. Results The large area of focal darkly stained regions by Von Kossa staining reduced obviously in alendronate group.The level of calcium content in aorta wall was significantly lower in the alendronate group than in the calcification group(67.33±19.86 μmol/g vs 114.3±23.23 μmol/g,P<0.05).The relative content of OPG mRNA in aortic wall was higher in the alendronate group than in the calcification group(P<0.01).The similar results was drawn by immuohistochemistry.OPG protein expression was similar to that for its mRNA expression. Conclusions Alendronate inhibited artery calcification by upregulating the expression of OPG.