Sexually dimorphic behavior after developmental exposure to characterize endocrine-mediated effects of different non-dioxin-like PCBs in rats

Abstract

Many chemicals are known to exhibit endocrine activity and affect reproductive functions in vertebrates and invertebrates. Endocrine effects include influences on sexual differentiation of the brain during development and reproductive and non-reproductive behavior in adult offspring. We previously demonstrated that developmental exposure to a mixture of polychlorinated biphenyls (PCBs) which was reconstituted according to the congener pattern found in human breast milk caused feminization of sweet preference as a sexually dimorphic behavior in adult male rats, following decreases in aromatase activity in the brain of newborn male pups. This result may be due to dioxin-like or non-dioxin-like (NDL) PCBs and their respective effects on steroid hormones. The aim of the present experiments was to determine if exposure to highly purified NDL-PCBs (to remove Ah receptor active contaminants) also results in alteration of sweet preference. Pregnant rats were orally exposed to PCB52 (6 dose groups, total dose of 0-3000mg/kg body weight) or PCB180 (6 dose groups, total dose of 0-1000mg/kg body weight). In a further experiment rat dams were treated with equimolar doses of PCB74 or PCB95 (total dose, 760μmol/kg body weight, corresponding to 229mg/kg or 248mg/kg body weight of PCB74 and PCB95, respectively). Adult male and female offspring were given a choice between a bottle of saccharin solution (0.25%) and a bottle of tap water on five consecutive days. Control females consumed approximately twice as much sweetened solution compared with control males, thus, demonstrating sexual dimorphism of this behavior. Only non-significant reduction of sweet preference was found at the top dose level in female offspring after exposure to PCB52. Female offspring exposed to PCB180 exhibited signs of supernormal behavior as illustrated by increased saccharin consumption at intermediate dose levels. Decreased sweet preference was observed in females after developmental PCB74, whereas males were unaffected. Only PCB95 increased saccharin consumption in exposed males, leading to decreased sexual dimorphism of this behavior and behavioral feminization. The results demonstrate that different NDL-PCBs exhibit differential effects on sexually dimorphic behavior and that feminization occurs after removal of Ah receptor active contaminants. Comparison with data from the literature reveals little evidence for a relation to anti-androgenic activity of the studied NDL-PCBs.

Keywords: Endocrine disruption; Polychlorinated biphenyls; Rat; Sexually dimorphic behavior; Sweet preference.