Production of new trabecular bone in osteopenic ovariectomized rats by prostaglandin E2

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Abstract
Serum chemistry and bone morphometry of the proximal tibial metaphysis were performed in 3-month-old double fluorescent-labeled, female Sprague-Dawley rats subjected to bilateral ovariectomy or sham surgery for 4 months prior to treatment with 0, 0.3, 1, 3, or 6 mg of prostaglandin E2 (PGE2)/kg/day subcutaneously for 30 days. The 4-month postovariectomized rats possessed an osteopenic proximal tibial metaphysis with 7% trabecular area compared with controls (19%). PGE2 treatment elevated osteocalcin levels and augmented proximal tibial metaphyseal bone area in ovariectomized and sham-operated rats. Osteopenic, ovariectomized rats treated with 6 mg PGE2/kg/day for 30 days restored bone area to levels of agematched sham-operated rats. Morphometric analyses showed increased woven and lamellar bone area, fluorescent-labeled perimeter (osteoblastic recruitment), mineral apposition rate (osteoblastic activity), bone formation rate (BFR/BV), and longitudinal bone growth. These dramatic bone changes were all significantly increased at the doseresponse manner. This study showed that in vivo PGE2 is a powerful activator of bone remodeling, it increases both bone resorption and bone formation, and produces an anabolic effect by shifting bone balance to the positive direction. Furthermore, PGE2-induced augmentation of metaphyseal bone area in ovariectomized rats was at least two times greater than in sham-operated rats.