AIM: To investigate the skeletal effects of total tanshinone in ovariectomized rats by analyzing cancellous bonehistomorphometry of fourth lumbar vertebrae (LV4) and proximal tibial metaphyses (PTM). METHODS: Four-month-old Sprague-Dawley female rats were sham-operated and treated with vehicle or ovariectomized and treatedwith either vehicle, total tanshinone (200 mgkg-1d-1, equivalent to 35 gkg-1d-1 of tanshinone II A and 16 mgkg -1d-1 ofcryptotanshinone), or 17a-ethynylestradiol (30 gkg-1d-1 as positive treatment group) starting one day post-sur-gery for 10 weeks. Double in vivo fluorochrome labeling was administered to all rats. The undecalcified longitu-dinal LV4 and PTM sections were cut and stained with Goldners Trichrome (4-m thickness) or unstained (8-mthickness) for the bone histomorphometric analysis. RESULTS: A significant decrease in trabecular bone volume(BV/TV) and trabecular number (Tb.N) and a significant increase in osteoclast surface (OCS/BS) and mineralizingsurface (MS/BS) were found in both LV and PTM of vehicle-treated OVX rats compared with sham controls.Tanshinone completely prevented the decreases in BV/TV and Tb.N and the increase in OCS/BS in the LV4, andpartially prevented the decreases in BV/TV and Tb.N in the PTM of OVX rats. In addition, tanshinone increasedtrabecular thickness (Tb.Th) whereas it did not alter MS/BS. Moreover, tanshinone had no effect on uterine weightand body weight of OVX rats. Estrogen treatment increased BV/TV and Tb.N and decreased OCS/BS, but, alsomarkedly decreased MS/BS and increased uterine weight in OVX rats. CONCLUSION: The current study demon-strated that the adequate supply of tanshinone prevented OVX-induced cancellous bone loss in rats through inhibi-tion of elevated bone resorption. AIM: To investigate the skeletal effects of total tanshinone in ovariectomized rats by analyzing cancellous bone histomorphometry of fourth lumbar vertebrae (LV4) and proximal tibial metaphyses (PTM). METHODS: Four-month-old Sprague-Dawley female rats were sham-operated and treated with vehicle or ovariectomized and treated with either vehicle, total tanshinone (200 mgkg-1d-1, equivalent to 35 gkg-1d-1 of tanshinone II A and 16 mgkg-1d-1 ofcryptotanshinone), or 17a-ethynylestradiol (30 gkg- -1 as positive treatment group) starting one day post-sur-gery for 10 weeks. Double in vivo fluorochrome labeling was administered to all rats. The undecalcified longitu-dinal LV4 and PTM sections were cut and stained with Goldners Trichrome (4-m RESULTS: A significant decrease in trabecular bone volume (BV / TV) and trabecular number (Tb.N) and a significant increase in osteoclast surface (OCS / BS) and mineralizingsurfa ce (MS / BS) were found in both LV and PTM of vehicle-treated OVX rats compared with sham controls. Tennessein completely prevented the decrease in BV / TV and Tb. N and the increase in OCS / BS in the LV4, andpartially prevented the decrease in BV / TV and Tb. N in the PTM of OVX rats. In addition, tanshinone had no effect on uterine weight and body weight of OVX rats. Estrogen treatment increased BV / TV and Tb.N and decreased OCS / BS, but, alsomarkally decreased MS / BS and increased uterine weight in OVX rats. CONCLUSION: The current study demon-strated that the adequate supply of tanshinone prevented OVX- induced cancellous bone loss in rats through inhibi-tion of elevated bone resorption.