Abstract: 【Abstract】Objectives To investigate mechanism of NFATcl in bone loss in a pastmenopausal osteoporosis(PMO)rat mode with ovarletomy(OVX) , and to explore the protective effects of exogenous estrogen in bone tissue. Methods The three months Wistar rats were randomly divided into sham operation group, OVX group, and OVX+E2 group and 10 rats in each group. In the OVX+E2 group, 17β-E2 was injected subcutaneously and the other two groups were given the same volume of normal saline. The of NFATcl in bone tissue were measured after 16 weeks. The bone mineral density (BMD), the fraction of bone tissues(BV/IV), The thickness of the trabecular bone (Tb.Th), number of trabecular bone (Tb.N) and thetrabecular spacing (Tb.SP) were measuredusing Micro-CT analysis, and serum E2 level was determined by ELISA. Results The OVX+E2 group and sham operation group compared with the OVX group, the levels of BMD, BV/TV, Tb.Th, Tb.N and serum E2 were significantly increased, the level of Tb.SP and NFATcl were significantly decreased. Conclusion Estrogen may prevent bone loss by decreasing NFATcl in OVX rats．

Key words: Estrogen, NFATcl, osteoporosis.