Evaluation of the effects of deltamethrin on the fetal rat testis

Pregnant Sprague-Dawley rats were administered deltamethrin, at doses of 0.1, 1, 5, or 10 mg/kg/day, or di-n-hexyl phthalate (DnHP) (250 mg/kg/day), by gavage, from gestation day (GD) 13 to 19. Maternal toxicity was observed at 10 mg/kg/day, as evidenced by transient clinical signs of neurotoxicity and reductions in body weight, body weight gain and corrected weight gain. Deltamethrin had no statistically significant effect on the incidence of post-implantation loss, fetal weight or anogenital distance in the male fetuses. Unlike DnHP, deltamethrin induced no changes in the expression of several genes involved in cholesterol transport or in the steroid synthesis pathway in the testes of GD 19.5 male fetuses (SRB1, StAR, P450scc, 3HSD, P450 17A1, 17HSD). Fetal testicular levels of P450scc and P450 17A1 protein were also unaffected by deltamethrin. No statistically significant differences were observed in the ex vivo fetal testicular production of testosterone and androstenedione after deltamethrin exposure, whereas DnHP markedly reduced these parameters. Deltamethrin metabolite, 3-phenoxybenzoic acid, was detected in amniotic fluid. In summary, our results demonstrate that in utero exposure to deltamethrin during the period of sexual differentiation had no significant effect on the testosterone synthesis pathway in the male rat fetus up to a maternal toxic dose.