EFFECTS OF INTERMITTENT ADMINISTRATION OF PTH ON BONE MARROW CELLS IN CANCELLOUS BONE OF OVARIECTOMIZED RATS

「Abstract」Introduction : Intermittent treatment with human parathyroid hormone (hPTH) has been considered to stimulate bone formation and lead to increased bone mass. However, there are still unidentified points in the mechanisms of this action. We evaluated the influence of intermittent PTH treatment on cancellous bones and adipocytes. Materials and Methods : Ovariectomy (OVX) or sham-operation in mature female rats was performed. After four weeks administration of hPTH (1-34) (100 μg/kg, once a week) or its vehicle, the proximal tibia was harvested. Along with the conventional bone histomorphometry, fat histomorphometry and evaluation of proliferating cell nuclear antigen (PCNA) with immunohistochemistry were performed on the cancellous bone and bone marrow cells. Results : Administration of hPTH increased the cancellous bone volume by stimulating bone formation in both normal and OVX rats. In OVX rats, estrogen deficiency-induced increases in the adipocyte volume and number were attenuated by hPTH administration. The percentage of PCNA-positive cells in bone marrow increased in both normal and OVX rats by PTH administration. Conclusions : These results suggest that hPTH enhances a local regulating action that increases osteoblastogenesis and decreases adipocytogenesis in cancellous bone.