Background: Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants that have been defined as major environmental pollutants. While previous studies have found that PBDEs may enhance the levels of sex-steroid hormones, their effects on testosterone secretion from rat Leydig cells are unclear. This study investigated the effects and mechanisms of PBDE-710, a mixture of tetra- and penta-PBDEs, on testosterone biosynthesis in rat Leydig cells. Methods: Leydig cells from adult male rats were challenged with different concentrations of PBDE-710 (0.5-15 ng/ml) to evaluate the effects on testosterone steroidogenesis. Concentrations of testosterone and of cAMP and pregnenolone in medium were measured by radioimmunoassay (RIA) and by enzyme-linked immunosorbent assay, respectively. Nuclear translocation of protein kinase A α (PKAα) was determined by immunofluorence assay and western blot assay, and the mRNA expression of steroidogenic acute regulatory protein (StAR) was analyzed by quantitative real-time polymerase chain reaction. Results: In this in vitro study, PBDE-710 (5 or 15 ng/ml) increased basal testosterone secretion and cAMP production by 3- and 2-fold, respectively. The stimulatory effect was abolished by adenylyl cyclase inhibitor. Enzyme activity of CYP11A1, as determined by the pregnenolone concentration, was stimulated by PBDE-710 treatment. Furthermore, nuclear translocation of PKAα was increased by 20 and StAR gene expression was elevated by 4-fold after PBDE-710 treatment. Conclusions: These Results suggest that low concentrations of PBDE-710 could stimulate testosterone secretion by acting directly on Leydig cells to activate the cAMP pathway and increase expression of StAR.
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