Effect of subchronic exposure to tetradifon on bone remodelling and metabolism in female rat

This study investigates the effect of subchronic exposure to tetradifon, an organochlorine pesticide with an oestrogen-like structure, in female rat. A single cumulative dose of 2430 mg/kg BW was administrated orally for 12 female rats of 190 g BW. Twelve non-treated additional rats have served as controls. Animals were sacrificed after 6 and 12 weeks of treatment. We studied bone remodelling through histomorphometry and scanning electron microscopy (SEM) analyses. The serum and the right femora were used to determine phosphatase alkaline (AlkP) and/or calcium and phosphorus content. No sign of toxicity was observed until the end of the experiment. The SEM results revealed no structural alteration of the treated animal bone tissue. However, in both treated groups, we have noted an increase in the trabecular distance and a heterogeneous aspect of the endosteum that could be explained by bone-remodelling disturbance, with relative delay of ossification. Following histomorphomotric analysis, these results were coupled with significant increases in Tb.Th and OS/BS. Elsewhere, tetradifon intoxication increased significant serum AlkP level in the group treated for 12 weeks, which could be explained by an osteoblastic hyperactivity. Tetradifon intoxication decreased significantly bone calcium end phosphorus contents. Tetradifon seems not to exert major effects on bone remodelling. However, the osteoblastic hyperactivity could be explained by the oestrogen-like activity of tetradifon and its fatty metabolism. In fact, oestrogen inhibits bone remodelling, and enhances bone formation, which could result in an increase of the osteoid surface and explain the relative delay of ossification. To cite this article: R. Badraoui et al., C. R. Biologies 330 (2007). Cette étude s'intéresse aux effets de l'exposition subchronique au tétradifon, un pesticide organochloré présentant une structure semblable a celle de l'œstrogène, chez le rat. Une seule dose cumulative (2430 mg/kg PC) du produit actif a été administrée par voie orale dans l'eau du boisson chez 12 rates femelles. Douze autres rates, non traitées, ont servi de témoins. Les animaux ont été sacrifiés après 6 ou 12 semaines. Le remodelage osseux a été étudié par analyse histomorphométrique et étude au microscope électronique à balayage (SEM). Le sérum et le fémur droit ont été objectivés pour la détermination du taux de phosphatases alcalines (AlkP) et/ou des teneurs en calcium et en phosphore. Aucun signe de toxicité