ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of zoledronate acid on osteoclast differentiation and gene expression of calmodulin (CAM) and calmodulin-dependent protein kinase (CAMK)II.</p><p><b>METHODS</b>Receptor activation of nuclear factor κB ligand (RANKL) was used to induce differentiation of RAW264.7 cells into osteoclasts in vitro. The cells were divided into two groups, group A and group B. Both groups were treated with RANKL for 5 days, whereas group B was also treated with zoledronate for the last 2 days.Osteoclastogenesis and gene expression of CAM and CAMK II were examined.</p><p><b>RESULTS</b>In group B, the number of new-generated osteoclasts (≥3 nuclei), number and size of dentin resorption lacunaes were (23 ± 3) , (19 ± 2) and (4951 ± 223) µm(2) respectively, which were significantly lower than those [(44 ± 3) , (46 ± 1) and (13 331 ± 248) µm(2)] in group A (P < 0.01).mRNA and protein level of CAM and CAMK II were also significantly down-regulated in group B when compared with group A (P < 0.01) and the decrease was 26.7% and 37.2% respectively for CAM, 57.0% and 76.1% respectively for CAMK II.</p><p><b>CONCLUSIONS</b>Zoledronate acid could significantly inhibit formation and resorption function of osteoclasts. CAM and CAMKII may be involved in the inhibition process.</p>