ABSTRACT
Raw264.7 cells were incubated with receptor activator of NF-kappa B ligand (RANKL) and α-melanocyte stimulating hormone(α-MSH) for6 d.The amount of osteoclast cells were counted by tartrate resistant acid phosphatase staining and the acid phosphatase activity was assayed.The expressions of 5 melanocortin receptors (MCR) in Raw264.7 cells were determined by RT-PCR.The results showed that the number of osteoclasts in RANKL +α-MSH group was significantly increased compared with RANKL group (P ＜ 0.05),but there was no osteoclast formation in α-MSH group.Compared with control group and α-MSH group,the acid phosphatase activities were significantly increased in RANKL group and α-MSH+RANKL group (P＜0.05).All five MCRs were expressed in the Raw264.7 cells shown by RT-PCR.These results suggest that α-MSH may promote osteoclasts formation through RANK signaling pathway.