Coplanar PCBs Health Effects in the Rat: Dose-Effect Relationships and Reproductive Toxicity Endopoint

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(1) Single injection of 10 or 100 μg/kg of PCB 126 on gestation day (GD) 15 to the dams delayed vaginal opening (VO) of their offspring significantly. In contrast, daily exposure to PCB 126 delayed VO only at a dose of 3 μg/kg/day, although cumulative doses of PCB 126 until chorionic gonandotropin (CG) 15 in the 1 μg/kg/day-group were estimated as much larger than 10 μg/kg. In addition, while a single injection of PCB 126 reduced the number of corpus lutea (CL), daily exposure to 1μg/kg/day did not alter it. These findings indicate that daily exposure may diminish effects of PCB 126 on female offspring as compared to single injection on GD 15. (2) The effects of Co-PCBs on CYP1A1, CYP1A2 and CYP2B1/2 mRNA expression were investigated by semi quantitative RT-PCR analysis in rats. In utero exposure to PCB126 (3μg/kg) or PCB169 (30 μg/kg) induced CYP1A1 and CYP1A2 mRNA expression levels in the liver of both male and female offspring. Exposure to PCB126 (30 μg/kg) or PCB169 (30 μg/kg) to pregnant rats induced CYP1A1, CYP1A2 and CYP2B1/2 mRNA expression levels in the placenta. (1) Proteins in the plasma of the (1-, 3-, 6-, and 15-week-old) rats, which were exposed to PCB126 or PCB169 in the viviparous phase, were analyzed by micro 2-dimensional electrophoresis. The influence of exposure to Co-PCBs on complement components (C3 and C4) in the plasma was observed in the 6- and 15-week-old rats, which were prenatally exposed to Co-PCBs. When toxicity for reproduction and development was considered from the aspect of the influence of Co-PCBs on a living body as an end point, the inactive amount was estimated to be 1 μg/kg. (4) It was also revealed that the exposure in the viviparous phase and milk-mediated exposure of neonates influenced expression of CYP1A1, CYP1A2, and CYP2B1/2 mRNA in the liver and dynamic changes in the complement system of proteins in the plasma.