Abstract:The osteogenic activity of bovine lactoferrin has been proved that bovine lactoferrin could promote proliferation and differentiation of osteoblasts and inhibit apoptosis of osteoclast.The growth and development of bones depended on the balance between bone resorption and bone formation.Osteoblasts and osteoclasts were associated with bone formation and bone resorption，respectively.The effects of different concentrations of bovine lactoferrin （20，100，500 μg/mL）on the osteoblast and osteoclast activity and bone resorptive activity of osteoclast were studied by co-cultures of MC3T3-E1 cells and RAW264.7 cells （used at a ratio of 1：1）in this paper.Alkaline Phosphatase（ALP）activity was detected by ALP activity Assay Kit.The result showed that low concentrations of bovine lactoferrin inhibited ALP activity of osteoblasts，whereas middle and high concentrations of bovine lactoferrin could significantly promote ALP activity.By tartrate resistant acid phosphatase（TRAP）activity Assay Kit and the ELISA kits，it was found that low and middle concentration of bovine lactoferrin could promote the TRAP activity of osteoclasts，while high concentrations of bovine lactoferrin could sig nificantly inhibit the TRAP activity and the ratio of receptor activator of the NF-κB ligand （RANKL）and os－teoprotegerin（OPG）.Bone resorptive activity of osteoclast as evaluated on bone-mimetic plates was significantly inhibited by middle and high concentration of bovine lactoferrin.In general，these results indicated that high concentrations of bovine lactoferrin could not only promote osteoblasts activity，but also inhibit steoclasts activity and function in co-culture system.