Notoya et al. (146) cho thấy ipriflavone ức chế cả sự kích hoạt của osteoclasts trưởng thành và sự hình thành của osteoclasts mới. Khi ipriflavone được bổ sung vào unfractionated nuôi cấy tế bào xương có chứa osteoclasts trưởng thành từ xương đùi và xương chày của những con chuột sơ sin | Osteoclast Differentiation 207 144 reported that zinc increased the number of OCL but inhibited bone resorption in neonatal rats and OCL culture systems. Cadmium Chronic exposure to cadmium has been linked to bone loss 145 . Addition of cadmium to normal canine bone marrow cell cultures accelerated osteoclast differentiation from their progenitors and also activated the mature osteoclasts. Ipriflavone Notoya et al. 146 showed that ipriflavone inhibits both the activation of mature osteoclasts and the formation of new osteoclasts. When ipriflavone was added to unfractionated bone cell cultures containing mature osteoclasts from femur and tibia of newborn mice there was a decrease in the number of osteoclast-like TRAP-positive multinucleated cells and bone resorption. In contrast no increase in the number of TRAP-positive multinucleated osteoclasts was observed in the presence of vitamin D3. Furthermore Miyauchi et al. 147 recently demonstrated the presence of novel specific ipriflavone receptors that are coupled to Ca2 influx in OCL and their precursor cells that may regulate OCL differentiation function. pH Shibutani and Heersche 148 studied the effect of pH on osteoclast formation in neonatal rabbit osteoclast cultures. Osteoclast differentiation and proliferation were optimal at pH but decreased at pH . Arnett and coworkers 149 have extensively studied the effects of pH on osteoclast formation and osteoclastic bone resorption. Acidosis stimulates bone resorption by activating mature osteoclasts present in calvaria and inducing formation of new osteoclasts. Furthermore at low pH osteoclast formation is markedly enhanced in vitro compared to neutral pH levels. These data suggest a critical role for acid base balance in controlling osteoclast function 150 . These results imply that the pH of the bone microenvironment can affect osteoclast formation differentiation. Bone Matrix Factors Osteopontin OPN Osteopontin is an acidic phosphoprotein synthesized by
