PARENT SESSION
PT2 - Endocrine Disruption
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P569) Development of methods to estimate E2 antagonist in vivo using Medaka.
Koshio, Masaaki*,1, Tatarazako, Norihisa1, Kawabe, Kiyoshi1, Shiraishi, Fujio1, Morita, Masatoshi1, 1 National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan
ABSTRACT- In the present study, we attempted to develop methods to estimate antagonistic effects on estrogen by hydroxytamoxifen (HTx) considered as E2 antagonistic chemicals, using medaka.We measured viterogenin (Vtg) concentrations in supernatant of liver homogenate (Slh) in male medaka (60-90 days after fertilization) that had been exposed in HTx solutions (25, 100, 400 ppb: n=10 in each solution) containing E2 (50ppt) for 7days. Vtg in Slh of fishes exposed in 50ppt Es showed high concentrations. Vtg concentrations decreased as increment of HTx (25-400 ppb). Toxicity evaluated by measuring GST activity in Slh did not differ among controls (no E2 and no HTx, 50ppt E2 without HTx). Thus, decrease of Vtg concentrations in Slh by increment of HTx in solutions from 25 to 100 ppb is thought to indicate HTx effects as E2 antagonist. It suggests that this method is availabile for evaluating E2 antagonistic activity. Using this methods, we evaluated antagonistic effect of endocrine disrupting chemicals. We found that a few chemicals acts as the antagonist of E2 in vivo.
Key words: endocrine disruption, antagonist, Medaka, hydroxytamoxifen