Studies on the effects of dioxin/dioxin-like congeners on the ovarian function and morphology in the progeny.

Next results were obtained by this study.1) Dairy oral exposure of female rats to PCB126 from 2weeks before mating until weaning through spontaneous delivery induced direct adverse effects on the growth and gene expression in the ovary of their progeny.2) Single oral exposure of female rats to PCB126 at gestational day 15 decreased the number of oocytes shed at the first ovulation in the progeny, suggesting that the critical point of PCB126 toxicity on the ovary of the progeny might be after gestational day 15 in the rats.3) Single oral exposure of female rats to PCB 126 at gestational day 15 induced decreasing the number of pre-antral and/or antral follicles and impaired expression of the genes associated with steroid-genesis in the ovary, decreasing blood level of inhibin and estradiol, and increasing blood level of FSH in the progeny, suggesting that PCB 126 disturbed follicular growth and steroid production in the ovary of the progeny.4) From the fostering study, either in utero or lactational exposure to PCB 126 induced growth inhibition of the ovarian follicles and decreasing the number of oocytes shed at the first ovulation, but such adverse effects were much more obvious in the lactationally-exposed progeny.5) Single oral exposure to PCB 126 in 24-day-old rats had not any adverse effects on the growth of the large ovarian follicles and the first ovulation, indicating low sensitivity of the ovary at this age to PCB 126.6) It was confirmed that a laser microdissection technique was very useful for sampling and analysis of gene expression of the particular sites in the ovary for searching the target cells of PCB 126.

Next results were obtained by this study.1) Dairy oral exposure of female rats to PCB126 from 2weeks before mating until weaning through spontaneous delivery induced direct adverse effects on the growth and gene expression in the ovary of their progeny.2) Single oral exposure of female rats to PCB126 at gestational day 15 decreased the number of oocytes shed at the first ovulation in the progeny, suggesting that the critical point of PCB126 toxicity on the ovary of the progeny might be after gestational day 15 in the rats.3) Single oral exposure of female rats to PCB 126 at gestational day 15 induced decreasing the number of pre-antral and/or antral follicles and impaired expression of the genes associated with steroid-genesis in the ovary, decreasing blood level of inhibin and estradiol, and increasing blood level of FSH in the progeny, suggesting that PCB 126 disturbed follicular growth and steroid production in the ovary of the progeny.4) From the fostering study, either in utero or lactational exposure to PCB 126 induced growth inhibition of the ovarian follicles and decreasing the number of oocytes shed at the first ovulation, but such adverse effects were much more obvious in the lactationally-exposed progeny.5) Single oral exposure to PCB 126 in 24-day-old rats had not any adverse effects on the growth of the large ovarian follicles and the first ovulation, indicating low sensitivity of the ovary at this age to PCB 126.6) It was confirmed that a laser microdissection technique was very useful for sampling and analysis of gene expression of the particular sites in the ovary for searching the target cells of PCB 126.