[Action of eel calcitonin on bone tissue--experimental study on bone cell activity in fracture healing in rat].

The purpose of this study is to investigate effects of calcitonin (CT) on bone tissues in fracture healing. Rats were fractured at middle of the femur and given [ASU1,7] eel CT. Following biochemical changes in the serum and histological findings of bone tissue were demonstrated. At the early stage of fracture healing process, CT activated the periostal ossification and elevated serum level of alkaline phosphatase activity. At the stage of cartilagenous callus, the number of chondroclasts were decreased and the development of cartilagenous tissue to primary cancellous bone was inhibited. After this, number of osteoclasts was decreased and bone resorption due to osteoclasts was decreased and bone resorption due to osteoclasts were suppressed. By these process, remodelling at the fractured site was suppressed and serum alkaline phosphatase activity was maintained at a low level. But as for each osteocyte in this stage, CT gave rise to periosteocytic osteoplasis. It is clear that CT accelerates the fracture healing by activating the periostal ossification in the early stage, whereas the fracture healing is suppressed after the stage of cartilagenous callus formation.