Bone Mineral Density and Biomechanical Properties of Spine and Femur of Ovariectomized Rats Treated With Naproxen

Prostaglandins have been reported to mediate the effects of ovariectomy on bone loss. We studied the effect of naproxen, an inhibitor of production of prostaglandins, on ovariectomy-induced bone loss. One hundred forty female Wistar rats 4.5 months of age were divided into groups of baseline, sham operation (sham), sham treated with naproxen at 10 mg/kg per day (in food), and ovariectomy treated with naproxen or estrogen as intramuscular injection of estradiol at 0.2 mg/kg body weight per week. They were killed 3, 6, and 9 months postsurgery. Bone mineral density (BMD) of the lumbar spine (L1–4), femoral neck, midshaft, and distal metaphysis was determined using dual-energy X-ray absorptiometry (DXA) in vitro. The compressive test of the L1 vertebral body and torsional test of the left femur were performed. The right femoral neck and femoral midshaft were processed undecalcified for determining cross-sectional moments of inertia. Naproxen treatment partially prevented ovariectomy-induced loss or less gain in BMD, in a significant manner, in the femoral neck cortical area, and also in L1 compressive strength and stiffness. Estrogen fully prevented these ovariectomy-induced effects. Naproxen showed no effect on ovariectomy-induced improvement in femoral torsional strength and stiffness and cross-sectional moments of inertia. No statistically significant difference was found between naproxen-treated sham rats and untreated sham rats. The data suggest that naproxen partially prevents ovariectomy-induced osteopenia.