RALOXIFENE PRESERVES BONE STRENGTH AND BONE MASS IN OVARIECTOMIZED RATS

We investigated the effects of raloxifene, a nonsteroidal benzothiophene, on bone strength in ovariectomized rats and compared them with estrogen treatment. Sixty ovariectomized Sprague-Dawley rats were divided into three groups for treatment with orally dosed raloxifene (3 mg/kg), ethynyl estradiol (EE, 0.1 mg/kg), or vehicle. A fourth group of 20 rats that underwent sham ovariectomies and received vehicle was used for comparison. Treatments began 3 days after ovariectomy and continued for 6 months. Raloxifene treatment resulted in greater bone strength in the lumbar vertebrae (P < 0.05) and femoral neck (P < 0.01) and greater bone mineral density at the proximal tibia (P < 0.001) and lumbar vertebrae (P < 0.001) when compared with vehicle-treated ovariectomized animals. The positive effects on bone biomechanical properties from raloxifene treatment were not different than those associated with EE treatment. Raloxifene did not cause a significant increase in uterine weight, whereas EE treatment resulted in uterine weight increased 4-fold over vehicle-treated ovariectomized controls. Therefore, in rats, raloxifene has beneficial effects on bone biomechanics that are equivalent to those of EE treatment without substantial effects on the uterus.