Cytochrome c oxidase activity in preosteoclasts induced by experimental tooth movement

Cytochrome c oxidase activity was detected in preosteoclasts induced by experimental tooth movement. Mitochondria with reaction products of the enzyme in the inner membrane and outer compartment, which we classified as type 1 mitochondria, were observed in preosteoclasts. The number of type 1 mitochondria in the preosteoclasts, however, was distinctly fewer as compared with those in active osteoclasts described in our previous studies. Also, some of preosteoclasts adjacent to the bone surface contained more type 1 mitochondria than preosteoclasts separated from the bone surface. These results suggest that cytochrome c oxidase activity is closely related to functional differentiation of preosteoclasts, and additionally can be used as an indicator of functional differentiation from preosteoclast to osteoclast.