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RESPONSE OF JAPANESE MEDAKA TO 17B-ESTRADIOL: A TIME COURSE OF ENDOCRINE-MEDIATED EFFECTS
Citation:
Thompson, S. C. AND W H. Benson. RESPONSE OF JAPANESE MEDAKA TO 17B-ESTRADIOL: A TIME COURSE OF ENDOCRINE-MEDIATED EFFECTS. SETAC 20th Annual Meeting, Philadelphia, PA, 14-18 November 1999.
Description:
Estrogenic compounds have been measured in the aquatic environment in concentrations subsequently found to affect reproduction and development in fish. Further investigations have described several endocrine-mediated events that indicate exposure of organisms to estrogens and/or estrogen-mimicking compounds. Biomarkers such as vitellogin (VTG) induction, estrogen receptor number and expression, as well as plasma steroid concentrations are sensitive to and specific for exposure to estrogens. However, little is known about how these indicators change with time of exposure. In this regard, Japanese medaka were exposed to aqueous concentrations of 17b-estradiol (E2) ranging from 10 to 100,000 ng/L for 7, 14 or 21 days. Plasma VTG induction at all time points was significantly elevated above reference values form 100 to 100,000 ng/L E2. Maximal induction at 7 days (472 ng/L E2) was significantly greater than maximal induction at either 14 (193 ng/L E2) or 21 (287 ng/L E2) days of exposure. These data suggest a shift in plasma VTG concentrations over time which may be attributed to down regulation of VTG or transport of proteins from the plasma. Examination of changes in endocrine-mediated biomarkers over time is an important step to further elucidate mechanisms of developmental and reproductive toxicity observed with chronic exposure to endocrine modulating substances.