The Effects Of Polychlorinated Biphenyls And Polybrominated Diphenyl Ethers On The Growth And Gonad Development Of Xenopus Laevis

PCB and PBDE are two Classical endocrine disruptors, because of stable chemical property, they bioaccumulation and magnified with the increase of food chain degree. Many researches have indicated that PCB and PBDE exposure affect the reproductive system, nervous system and endocrine system. The affect of reproductive system received much concern. Both of PCB and PBDE could degenerate the male gonad of Xenopus laevis, and affect the male reproductive function. We use Xenopus laevis as the experiment model to investigate the effect of PCB and PBDE to the growth and gonadal development of Xenopus laevis.[Method] Xenopus laevis were exposed to several exposures in water from NF stage 46/47 to one month postmetamorphosis, Followed by another two months without exposure. 3 months postmetamorphosis, statistics the body weight, liver weight, and the gonads of frogs were examined in gross morphology and histology. Isolate the male gonad and brain, the total RNA were extracted and reverse transcription into cDNA. Amplification of the specific Gene of ER, AR, Aro, and statistics the expression levels compared with the control.[Result]1. Neither 5μg/L PCB-118 nor 5μg/L OH-PCB affect the body and liver weight of Xenopus laevis. The 5μg/L OH-PCB increased the percentage of female gonad but the 5μg/L PCB-118 had no effects. The histological observation suggested that neither PCB nor PBDE can change the histological structure of female gonad, but degenerate the testis. For example loosen the structure of testis and appeared the early oocytes in testis. OH-PCB exposure induced mature oocyte in testicular tissue.2. PBDE-209 exposures delayed the metamorphosis time, reduced the body weight, but have no effect on liver weight of Xenopus laevis. In addition, PBDE-209 increased the percentage of testicular-oocyte in male gonad, and delayed the testis development: there are few spermatogonias or a lot of spermatogonias but few spermatocytes and sperm cell. 10μg/L PBDE-209 exposure induced mature oocyte in testis.3. 0.5μg/L PCB-118 exposure increased the somatic cell in testicular tissue. But 0.5 μg/L PBDE-209 exposure caused dying of sperm cells. PCB and PBDE exposure also induced dying sperm cells. Gene expression suggested that 0.5μg/L PCB-118 increased the AR and Aro expression, but no effect on ER expression. PBDE-209 exposure increase the ER, Aro expression but no effect on AR expression. PCB and PBDE exposure only induced the AR expression and had no effect on ER, Aro expression.[Conclusion] OH-PCB and PCB-118 had the effect to feminizing the gonad of Xenopus laevis. PBDE has toxicity to growth and development of Xenopus laevis, and also disrupted the male gonad with feminization effect. Low concentration of PCB and PBDE mainly exhibit toxicity to the reproductive system. Both PCB and PBDE can affect the AR, ER, Aro gene expression.