Dose-dependent alterations in androgen-regulated male reproductive development in rats exposed to di(n-butyl) phthalate during late gestation

Di(n-butyl) phthalate (DSP) is a commercially important plasticizer and ubi quitous environmental contaminant. Since previous, limited dose-response st udies with DBP that reported alterations in male reproductive development a nd function failed to establish a NOAEL (no-observed-adverse-effect level), an extensive dose-response study was conducted. Pregnant CD rats were give n DBP by gavage at 0, 0.5, 5, 50, or 100 mg/kg/day (n = 19-20) or 500 mg/kg /day (n = Il)from gestation day 12 to 21. In male offspring, anogenital dis tance was decreased at 500 mg DBP/kg/day. Retained areolas or nipples were present in 31 and 90% of male pups at 100 and 500 mg/kg/day, respectively. Preputial separation was not delayed by DBP treatment in males with normal external genitalia, but cleft penis (hypospadias) was observed in 5/58 rats (4/11 litters) at 500 mg/kg/day. Absent or partially developed epididymis (23/58 rats in 9/11 litters), vas deferens (16/58 animals in 9/11 litters), seminal vesicles (4/58 rats in 4/11 litters), and ventral prostate (1/58 a nimals) occurred at 500 mg/kg/day. In 110-day-old F-1 males, the weights of the testis, epididymis, dorsolateral and ventral prostates, seminal vesicl es, and levator anibulbocavernosus muscle were decreased at 500 mg/kg/day. At 500 mg/kg/day, widespread seminiferous tubule degeneration was seen in 2 5/58 rats (in 9/11 litters), focal interstitial cell hyperplasia in 14/58 r ats (in 5/11 litters), and interstitial cell adenoma in 1/58 rats (in 1/11 litters). For this 10-day prenatal (embryonic and fetal) exposure to DBP, t he NOAEL and LOAEL (lowest-observed-adverse-effect level) were 50 and 100 m g/kg/day, respectively. This is currently the lowest NOAEL described for th e toxicity of DBP.