Effects of dibutyl phthalate on testosterone biosynthesis in rats

  Objective   To investigate the effects of dibutyl phthalate(DBP)on testosterone biosynthesis and its related mechanism in rats.

  Methods   Six-week-old healthy male SD rats were randomly divided into 4 groups with 8 animals per group. DBP dissolved in peanut oil was administered by gavage at doses of 0, 250, 500, 1 000 mg/(kg·d). After 4-week DBP exposure, the animals were sacrificel with testis selected and weighed. Luteinizing hormone(LH), 17β estradiol(17β-E₂), testosterone(T)were detected by radioimmunoassay. The relative expression levels of cholesterol sid-echain cleavage enzyme(P450scc)mRNA and 3beta-hydroxysteroid dehydrogenase(3β-HSD)mRNA were determined by RT-PCR.

  Results   LH levels in serum were not significantly changed, whereas 17βE₂ in serum elevated noticeably induced by DBP. T levels in testis homogenate and in serum reduced signifcantly in 500 and 1 000 mg/(kg·d)groups. Furthermore, mRNA expression was downregulated for P450scc and 3β-HSD following DBP exposure. Linear correlation and regression revealed that there were obvious relationships between dosages(logarithm)and the expression of P450scc mRNA and 3β-HSD mRNA.

  Conclusion   Leydig cells may be one of the major target cell affected by DBP. It is likely that downregulation of T biosynthetic enzymes mRNA may be key factors contributing to the decrease of T concentration. Secondly, The increase of 17βE₂ disordered physiologic balances of hypothalamic-pituitary-testis axis(HPTA)and local modulation in testis.