Joint neurodevelopmental and behavioral effects of nonylphenol and estradiol on F1 male rats.

The purpose of present study is to examine whether gestational exposure of two major environmental endocrine-disrupting chemicals, nonylphenol (NP) and estradiol (E2), would affect nervous system development of offspring rats and explore the joint effects of NP and E2. After impregnation, dams were assigned to seven groups. The first and second groups received gavage with NP at dose levels of 50 mg/kg/day (NP-L) and 100 mg/kg/day (NP-H); the third and fourth groups were gavaged with E2 at dose levels of 10 μg/kg/day (E2-L) and 20 μg/kg/day (E2-H); the fifth and sixth groups were gavaged with joint NP and E2 [NP 50 mg/kg/day + E2 10 μg/kg/day (NP-E2-L) and NP 100 mg/kg/day+E2 20 μg/kg/day (NP-E2-H)] dissolved in groundnut oil; and the seventh group was orally administered with groundnut oil alone (vehicle control; 2 ml/kg/day), respectively, daily from gestational days 9 to 15 (transplacental exposures). Compared to the control, exclusive NP and E2 treatment groups, joint exposure to NP-E2-L and NP-E2-H has both produced a significant decrease in mean litter size and number of live pups per litter in dams; Offspring rats spent more time to perform cliff-drop aversion reflex, surface righting reflex, air righting reflex, auditory startle, and visual placing; In Morris water maze task, an increased escape latency was presented in offspring rats; In step-down avoidance test, offspring rats jointly exposed to NP and E2 spent more reaction time. Decrease in acetylcholinesterase activity and increase in choline acetyltransferase activity were observed in the hippocampus of offspring rats. Gestational joint exposure to NP and E2 might induce nervous development impairment of offspring rats. Moreover, additive toxic effects of NP and E2 on nervous development have been identified among offspring rats as well.