Developmental toxic potential of di-n-propyl phthalate administered orally to rats.

The objective of this study was to evaluate the developmental toxic potential of di-n-propyl phthalate (DnPP) in rats. Pregnant Sprague-Dawley rats were given DnPP at doses of 0 (olive oil), 0.5, 1 and 1.5 g kg⁻¹ per day, by gavage, on gestation days 6-20. Benchmark doses were calculated for the effects of DnPP on fetal weight and anogenital distance of the male fetuses. Maternal body weight gain was significantly reduced at 1.5 g kg⁻¹ per day, over gestation days 6-9. DnPP-treated dams also showed a statistically significant increase in liver weight and a mild but statistically significant peroxisomal enzyme induction at 1 or 1.5 g kg⁻¹ per day. Male and female fetal body weights were significantly reduced at 1.5 g kg⁻¹ per day. There was a statistically significant decrease in the anogenital distance of the male fetuses at 1 and 1.5 g kg⁻¹ per day, and three males (of 75) showed malpositioned testis at the high dose. The mean percentage of fetuses per litter with cervical and thoracic rudimentary ribs was significantly increased at 1 and 1.5 g kg⁻¹ per day. Delayed ossification was seen at 1 g kg⁻¹ per day (phalanges) and 1.5 g kg⁻¹ per day (hyoid, sternebrae, and phalanges). No treatment-related effects on prenatal viability or on fetal external or visceral malformations or variations were observed at any dose. Thus, there was no evidence of teratogenicity up to the high dose of 1.5 g kg⁻¹ per day. The no-observed-adverse-effect level (NOAEL) for developmental toxicity was 0.5 g kg⁻¹ per day.