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Conversion of estrone to estradiol in male fathead minnows: Implications for assessing risk
Citation:
Feifarek, D., E. Randolph, R. Milsk, J. Cavallin, S. Poole, T. Saari, K. Jensen, B. Blackwell, Dan Villeneuve, AND G. Ankley. Conversion of estrone to estradiol in male fathead minnows: Implications for assessing risk. SETAC North America, Orlando, FL, November 06 - 10, 2016.
Impact/Purpose:
not applicable
Description:
Estrogens are frequently observed in aquatic environments associated with anthropogenic influence, such as agricultural runoff and wastewater treatment effluent. While 17â-estradiol (E2) is the most potent naturally-occurring estrogen, estrone (E1) is often found at higher environmental concentrations. However, exogenous sources of E1 could potentially be converted to the more potent E2 through the action of endogenous 17â-hydroxysteroid dehydrogenase activity, specifically, the 17â-hydroxysteroid dehydrogenase type 1 isoform (HSD17B1). Observation of increased plasma E2 concentrations without measureable changes in aromatase (cytochrome P45019a) expression in male fish caged in ambient waters containing elevated concentrations of E1, but low or non-detectable concentrations of E2, suggested this may be occurring in the field. If so, exogenous E1 may have a greater impact on reproductive function in aquatic vertebrates than previously assumed. The present study was conducted to evaluate this hypothesis. Male fathead minnows (Pimephales promelas) exposed to aqueous concentrations of 16.7, 50, and 150 ng E1/L in the laboratory exhibit significantly (p<0.05) elevated plasma E2 concentrations relative to control. Plasma testosterone (T) was elevated at a low E1 exposure concentration (1.8 ng E1/L) and depressed at the highest level of exposure (150 ng E1/L). Additionally, vitellogenin (VTG) mRNA expression was significantly elevated at concentrations of 50 and 100 ng E1/L. Results suggests that when assessing potential risks of environmental estrogen mixtures to fish, it may be necessary to assume that potency of measured E1 is, in fact, equivalent to that of E2.