Endocrine disruptors are hormone mimics that modify hormonal action in humans and wildlife. Endocrine disruptors are hormone mimics that modify hormonal action in humans and wildlife. They bind to the estrogen receptor or androgen receptor, mimic natural hormones and influence vital endocrine functions. Recently, environmentally induced alterations of endocrine function in fishes are well being studied and sex reversal or intersexuality are known to be induced following exposure of egg or juvenile fish to environmental estrogens during the early part of a fishes life.
Vitellogenin is the precursor of yolk protein and secreted by the liver of female as well as male fish in response to estrotgenic compoinds, so the protein induction means the exposure of endocrine distupting chemicals.
In this study, endocrine disrupting effects of some chemicals were investigated on freshwater fishes and frog. When exposed to DES and nonylphenol, obsessive vitellogenin production and it's accumulation in kidney introduced inhibition of growth and increase of lethality to tested carp. And alteration of testis tissue leaded inhibition of spermatogenesis and destruction of lobule, also. By treatment of E2, EE2, bisphenol A and nonylphenol to male fishes including crucian carp, carp, and bluegill, RT-PCR for vitellogenin expression and cDNA sequences identification of vitellogenin in these fishes were performed. Wild type O. sinensis was exposed to EE2 and bisphenol A to assess vitellogenin induction and using ELISA method, its expression was measured. And effluents of sewage treatment were treated to evaluate estrogenic effects of complex media. Also, field studies were performed to monitor of EDC exposure for wild chinese medaka in lncheon, Kyunggi and Chungcheong province. In Xenopus lawis, DEHP and E2 treatments were found to lead vitellognin expreesion in male and inhibition of spermatogenesis.
Because the final destination of chemicals exposed to environment is water, exact evaluation of endocrine disruption in fish and amphibian is needed to manage of endocrine disrupting chemicals in environment. For this reason, ministry of environment has launched and performed monitoring projects for several years. But this monitoring project focus on the vitellogenin measurement using ELISA in blood and ovo-testis observation .
In this study, vitellogenin gene sequnences were identified in carp, crucian carp and bluegill. And by using this sequence-based RT-PCR method, the possibility of vitellogenin mRNA expression was examined as a biomarker for the screening of environmental estrogenic chemicals. And also, instead of orange-red medaka, wild type chinease medaka was used for the several exposure experiments and so its possibility as test organism for monitoring stream water was evaluated.
Meanwhile if the results of experiment using Xenopus laevis can be applied to wild type bull frog and frog, the vitellogenin measurement by RT-PCR and ELISA can be used as a potential biomarker for screening and assessing the environmetal estrogens in frog in wildlife.
