| Project/Area Number |
11839006
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Institution | NIIGATA UNIVERSITY |
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Principal Investigator |
HAMAGUCHI Satoshi FACULTY OF SCIENCE, NIIGATA UNIVERSITY, PROFESSOR, 理学部, 教授 (20126444)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAIZUMI Mitsuru FACULTY OF SCIENCE, NIIGATA UNIVERSITY, PROFESSOR, 理学部, 教授 (40175360)
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| Project Period (FY) |
1999 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2001: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2000: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1999: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | MEDAKA / SEX REVERSAL / SEX DIFFERENTIATION / ENDOCRINE DISRUPTOR / VITELLOGENIN / ビテロゲニン / 野生メダカ / 寿命 / 精巣 / 環境ホルモン |
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| Research Abstract |
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.
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