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Conversion of estrone to 17â-Estradiol: A potential confounding factor in assessing risks of environmental estrogens to fish
Citation:
Tapper, M., R. Kolanczyk, C. LaLone, J. Denny, AND G. Ankley. Conversion of estrone to 17â-Estradiol: A potential confounding factor in assessing risks of environmental estrogens to fish. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 39(10):2028–2040, (2020). https://doi.org/10.1002/etc.4828
Impact/Purpose:
This study addresses the environmental and health problem of the effect on aquatic species of endocrine disrupting chemicals in the environment. An endocrine disrupting chemical interferes with the organism’s endocrine system by mimicking the activity of the normal hormones found with the organism. This may produce adverse reproductive, developmental and neurological effects. From the standpoint specifically of E1, our study clearly shows the potential for underestimating the risk of this common environmental estrogen to aquatic vertebrates. In the absence of biotransformation, the estrogenic potential of E1 is low, at around 3 to 6% of the potency of E2. However, the apparent estrogenic potency of E1 can be increased by an order-of-magnitude through the formation of E2. Furthermore, the 17âHSDs likely responsible for biotransformation of E1 to E2 in the two salmonid species evaluated in this study are probably well-conserved across most bony fishes, suggesting that this biotransformation would be a wide-spread phenomenon.
Description:
Feminization of male fish and the role of endocrine-active chemicals in this phenomenon has been an area of intense study for many years. Estrone (E1), a natural steroid, is found in aquatic environments sometimes at relatively high concentrations. However, E1 has been less thoroughly studied than 17â-estradiol (E2) or 17á-ethynylestradiol (EE2) due in part to a relatively lower potency in metabolically-limited estrogen receptor (ER) binding/activation assays. Recent evidence suggests that in vivo biotransformation of E1 to E2 may occur in fathead minnows (Pimephales promelas) residing in environments with high concentrations of E1, such as near wastewater treatment plants. The enzymes likely responsible for this biotransformation, 17â-hydroxysteroid dehydrogenases (17âHSDs), have been well characterized in mammals but to a lesser extent in fish species. In the current study, a novel systematic analysis of amino acid sequence data from the National Center for Biotechnology Information database demonstrated that multiple 17âHSD isoforms (1,3,7, and 12A isoforms) are conserved across different fish species. Experimentally, we showed that metabolically-active hepatic cytosolic preparations from two commercially and culturally important salmonid species, rainbow trout and lake trout, biotransformed E1 to E2 to a degree sufficient to alter results of competitive ER binding assays. These results from in silico and in vitro analyses indicate E1 and biotransformation may play a significant role in the feminization of a variety of fish species in contaminated aquatic environments.
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DOI: Conversion of estrone to 17â-Estradiol: A potential confounding factor in assessing risks of environmental estrogens to fish