CONSTRUCTION OF A MONITERING SYSTEM OF ENDOCRINE DISRUPTING SUBSTANCES USING MEDAKA

本项目的实施是为了开发一个可靠的系统，用于使用青鳉测试环境内分泌干扰物的影响。青我们可以重申青鳉作为雌激素物质存在的测试生物的有效性，不仅作为实验室动物，而且作为野生动物。得到以下结果.使用Y染色体上的遗传标记，可以准确区分特定个体的遗传性别。从野生青鳉的筛选中，我们发现了3个与性别分化有关的突变。内分泌干扰物诱导的性反转也可以被识别.阐明了野生青鳉血清中卵黄原蛋白含量的年变化规律。雌鱼卵黄蛋白原在春、夏两季含量较高，秋、冬两季含量较低。在男性，我们不能检测到卵黄蛋白原全年。这些结果表明，野生青鳉的卵黄蛋白原含量可以很好地指示环境中雌激素类物质的污染程度.用性逆转率和卵黄蛋白原含量两个指标评价了青鳉自交系对雌激素的敏感性。性激素诱导的性反转率因品系而异。同源株和重组株的使用阐明了性别逆转率的差异可归因于与Y染色体上的性别决定基因密切相关的遗传因素。我们还研究了雌激素处理的鱼血清中卵黄蛋白原含量的剂量-反应关系和时间过程的变化。处理后7天内，雄性鱼中出现卵黄蛋白原，并确定了明确的剂量依赖关系。不同品系间卵黄蛋白原含量无明显差异。

The present project was performed in order to develop a reliable system for testing the effects of environmental endocrine disruptors using medaka. Oryzias latipes. We could reaffirm the validity of the medaka as a test organism for the presence of estrogenic substances, not only as a laboratory animal but also as a wild life. The following results were obtained.1. Using a genetic marker on Y chromosome, the genetic sex of a given individual become able to be distinguished exactly. From the screening of wild medaka by this marker, we identified 3 mutations as to the sex differentiation. The sex reversal induced by endocrine-disruptors can also be identified.2. Annual change of vitellogenin content in the serum of wild medaka was clarified. In females, vitellogenin was high in spring and summer, and low in autumn and winter. In males, we could not detected vitellogenin throughout the year. These results indicate that the vitellogenin content of wild medaka is a good indicator of the contamination of estrogenic substances to environment.3. Using two different indicators, the rate of sex reversal and the vitellogenin content, the sensitivity to estrogens of inbred medaka strains was evaluated. The rates of the sex-reversal induced by sex steroids varied among strains. The use of congenic strains as well as recombinant strains clarified that the difference in the rate of sex-reversal can be attributed to a genetic factor that is strongly linked to the sex-determining gene on Y chromosome. We also examined the dose-response relationship and a time-course change of the vitellogenin content in the serum of fish treated with estradiol. Vitellogenin appeared in male fish within 7 days of treatment and a definite dose-dependent relationship was identified. There was no obvious difference in the content of vitellogenin among strains used.