Effects Of 2,2'5,5'-Tetrachlorobiphennyl And Estradiol On Chicken Reproductive Function

The overall objectives of this research were to investigate the effects of 2,2'5,5'-tetrachlorobiphenyl(PCB52) and estradiol on chicken reproduction function using primordial germ cells(PGCs) proliferative migration, and spermatozoa interact with the ovum by enumerating the spermatozoa which penetrate the inner perivitelline layer over the germinal disc.PCBs, including PCB52, are persistent, synthetic, lipophilic, toxic chemicals that gained widespread industrial use because of their physical and chemical properties. There are many reports that PCB52 had adverse effects on wild animal and human by its estrogen-like function. Estrogens, including estradiol, which are used as drugs for humans and animals, are a group of endocrine disruptors.To study the PCB52/estrogen effects on chicken reproductive efficiency, chicken embryo and spermatozoa were exposed to 2,2'5,5'-tetrachlorobiphenyl(PCB52) and estradiol during embryonic incubation and pre-insemination, respectively.1. Fertilized eggs were treated with 17beta-estradiol (E₂) at stage X (0 day of incubation), stages 8-10 (incubation 30 hours), and 13-15 (incubation 132 hours). Then the changes of PGC number were measured in the different later developmental stages. At stages 8-10, there was an increase in the number of PGCs in the E₂-treated group, but this difference was not statistically significant (P= 0.076). E₂ had no effect on the PGC number at stages 13-15 (P=0.39), and no effect on the cell number at stages 28-30 (P=0.24). In area pellucida, E₂ had not significant effect on the cell number at these stages. At stages 13-15, E₂ treatment had no effect on the PGC number at stages 13-15 (P=0.47), and also no effect on PGC number at stages 28-30 (P=0.34). At stages 28-30(incubation 140 hours), E₂ exposure showed no significant effect on PGC number (P=0.26).The blastoderm of chicken embryos was injected with PCB52 and E₂ prior to incubation and then the number of PGCs was determined during its migration and development. The number of PGCs in germinal crescents in PCB52-treated groups was slightly decreased (P=0.068), but it was reduced significantly at stages 13-15 and 28-30 (P<0.01,respectively) compared with controls. No obvious effects on PGC migration were observed with E₂ treatments. In area pellucida, PCB52 decreased significantly the area PGC number (P<0.05).These results indicated that the affect of PCB52 on chicken PGC migration and proliferation is starting from reducing area pellucida PGC number, and this adverse is a toxic instead of its estrogen-mimicking effect. This suggested that PGC estrogen receptors were not expressed in early developmental chickenembryos, since many of the effects of estrogens are mediated through binding to the estrogen receptor.2. Chicken spermatozoa were treated with PCB52 and E2 prior to insemination. The sperm quality indexes were evaluated and the sperm egg interaction was measured by enumerating the spermatozoa that penetrate the inner perivitelline layer over the germinal disc.Spermatozoa treated with PCB52 and E2 at 37°C for 20min hydrolyse holes in the inner perivitelline layer from laid eggs in an in vitro assay. PCB52 reduced significantly the inner perivitelline layer holes (IPVL holes) , including germinal disc IPVL holes, nongerminal disc IPVL holes, the fertile period and fertility, compared with control. However, E2 had no significantly differente on these index. At the same condition there were not significantly different on sperm quality index such as motility, abnormality. These results indicated that the biomark of sperm : egg interaction was more sensitive than traditional biomarks.