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PW08 Aquatic Ecotoxicology II
(PW122) Physiological Influence of 17beta-Estradiol Secreted from Female Medaka on Male Medaka.
Kashiwada, Shosaku1, Kameshiro, Maiko1, Hinton, David2, 1 National Institute for Environmental Studies, Japan, Tsukuba, Ibaraki, Japan2 Duke University, Durham, NC, USA
ABSTRACT- It is well known vitellogenin (Vtg) is a remarkable biomarker for environmental estrogen effect on male fish. Regardless, vitellogenin is also known to be detected from serum and liver in male fish keep away from exogenous estrogen mimics. There are some causes to induce Vtg in male. 17Beta-estradiol (E2) secreted from female have been considered of Vtg inducers in male. In meanwhile, there is no available information on physiological E2 effects on male fish in general condition, except for Vtg induction and kidney damage in only case of high E2 and Vtg concentration. This study is designed to clarify physiological effects on male fish of E2 naturally secreted from female fish. Male medaka fish was reared with female medaka in ratio of 1: 4 (male: Female) at 26 C with 18/6 hours light and dark photoperiod. An E2 concentration in incubation water was measured every two days and incubation water was renewed. After seven days, all medaka were sacrificed, and serum and liver were removed, frozen in liquid nitrogen and reserved at −80 C until use. As a control male medaka was reared in the absent of female, and subjected to same way. Detected E2 concentrations were in ranges of 3-4 pg/mL and 32-60 pg/mL in incubation water of male and male/female, respectively. E2 concentration in water was 10-folds higher in male/female mixed condition. However, E2 concentration in serum of male in the present of female was as same as that of male in the absent of female. E2 concentration of female serum was 2,300 ng/mL, it was 1,000-folds higher than that of male. Vtg was detected in serum of male in the present of female at 230 ng/mL, although not detected in serum of male in the absent of female. Testosterone and its metabolite 11k-testosterone were measured, and these concentrations were reduced in serum of male in the present of female to less than half of male in the absent of female. Induction of CYP3A38 and CYP3A40, that are two isozymes of testosterone metabolic enzyme in medaka, also suppressed in liver. We will discuss about E2 effect on sex behavior at presentation.
Key words: E2, hormone disruption, medaka, vitellogenin
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