The effects of prostaglandin E2 in growing rats: Increased metaphyseal hard tissue and cortico-endosteal bone formation

Summary To assess the efficacy of PGE₂ in inducingin vivo bone formation, graded doses of prostaglandins E₂ were administered to 255 g rats. Histomorphometric analyses of selected sequential fluorescent-labeled bones of rats treated with 0,0.3, 1.0, 3, or 6 mg PGE₂/kg/d for 21 days showed that the doses of PGE₂ depressed longitudinal bone growth, increased growth cartilage thickness slightly, decreased degenerative cartilage cell size and cartilage cell production slightly, and increased proximal tibial metaphyseal hard-tissue mass markedly. Periosteal bone formation was depressed at the higher doses, and an early, slight depression in endosteal bone formation was also observed, along with a striking late increase in endosteal bone formation and in the formation of trabecular bone in the marrow cavity of the tibial shaft. The characteristics and magnitude of these responses were quite similar to those observed in our previous study of the effects of PGE₂ on weanling rats except for the delayed increase in cortico-endosteal bone formation.