Objective: To compare the effects of one year treatment of estrogen and tamoxifen, either alone or combined with fluoride on bone metabolism in ovariectomized rats.
Methods: One hundred and forty two virgin female Sprague-Dawley rats were ovariectomized (OVX) or sham operated at 6 months of age, and randomly divided into 7 groups (19 - 21 rats each): (1) sham-operated controls; (2) OVX vehicle controls; (3) estrogen group; (4) fluoride group; (5) tamoxifen group; (6) fluoride plus estrogen; (7) fluoride plus tamoxifen. The treatments lasted for one year. Bone mineral density (BMD) measurement, bone histomorphometry analysis (lumbar vertebrae) and biomechanical test (3-point-bending test on right femur) were performed before and after treatment. The histological change of uterus were also determined at the same time.
Results: (1) Twelve months of ovariectomy, the OVX group had significantly lower total body (279 mg/cm(2)), lumbar vertebra (232 mg/cm(2)) than all other groups (total body 286 - 298 mg/cm(2), lumber 251 - 266 mg/cm(2), P < 0.05). Estrogen group (216 mg/cm(2)) had higher BMD than tamoxifene group (195 mg/cm(2)) in midshaft of femur. (2) After 4 months of ovariectomy, only the two combination groups kept the maximum load (145 N) of right femur over the level of OVX group (118 N); after 12 months of treatment, the maximum load of OVX group [(108 +/- 13) N] was significantly different from all other groups (132 - 155 N); both maximum load and elastic load of estrogen group were significantly higher than that of tamoxifen group. (3) No evidence of dysmineralization was found by bone histomorphometry.
Conclusions: Estrogen has more potent effects on keeping bone mass and bone strength as compared with tamoxifene. The combined therapy (estrogen + fluoride or tamoxifen + fluoride) resulted in better bone strength than the single ones.