Three-generation experiment showed female C57BL/6J mice drink drainage canal water containing low level of TCDD-like activity causing high pup mortality

Abstract

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polychlorinated biphenyls (PCBs) and similar compounds are toxic to animals and humans. Based on a yeast reporter system, AhR-activating ligands similar in concentration to 2 ng/l of TCDD were detected in two canal waters in Guangzhou, China. In this study, a three-generation experiment was conducted to assess the reproductive and developmental risks associated with these waters in C57BL/6J female mice, including female reproduction, pup indices, reproductive hormone levels, and levels of AhR, ARNT, and CYP1A2 in the uterus. Similar reproductive toxic effects were produced in the offspring of mice that drank the canal water as would occur if they drank 2 ng/l/day TCDD. The major reproductive indices that were affected included mating time and gestation length over all the generations. A striking finding is the TCDD (2 ng/l) and the water samples significantly reduced Day 4 pup survival rates in the F2 and F3. Both TCDD exposure and drinking canal water decreased estradiol-17β (E2) levels in the multiparous females and decreased follicle-stimulating hormone (FSH), luteinizing hormone (LH) and E2 levels in the virgin females. Immunochemical staining revealed that the AhR and CYP1A2 positive signals were enhanced, and the ARNT positive signal was weakened in the uteri of mice drinking water with TCDD (2 ng/l) and the canal water samples. These results imply that the canal water contains AhR ligands that could induce similar toxic effects as do low levels of TCDD. Exposure to these contaminants can significantly impair the reproductive health of female mice. Considering this canals are open directly to Pearl River, whether these effects could be caused in human reproduction and development warrants further study.