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PT13 Aquatic Ecotoxicology I
(PT194) Multigenerational responses of Daphnia magna to Ethynylestradiol and Faslodex.
Clubbs, R1, Brooks, B1, 1 Baylor University, Waco, TX
ABSTRACT- Growing evidence supports that select chemicals disrupt or modulate normal functions of aquatic invertebrate endocrine systems. Ethynylestradiol (EE2), a synthetic estrogen, is the most potent component of oral contraceptives, which are among the most widely prescribed pharmaceuticals. ICI 182,780, or Faslodex, is a novel antiestrogen designed for use in human breast cancer treatment. A broad range of EE2 concentrations have been reported in raw sewage, and it appears that EE2 and other pharmaceuticals are potentially released continuously from wastewater treatment plants. Although effects of EE2 and Faslodex have been examined in vertebrates and select invertebrates, limited studies have assessed potential multigenerational effects, which are more representative of environmentally realistic exposure scenarios. Further, considerable uncertainty exists to the mechanisms by which these and other pharmaceuticals act in invertebrates. The objective of this study was to investigate effects of a mammalian estrogen receptor agonist (EE2) and antagonist (Faslodex) on the transgenerational life-history of a model invertebrate, Daphnia magna. Chronic responses (e.g., mortality, fecundity, molting, growth, sex ratios, vitellin, intrinsic rate of population growth) were assessed for F0 and F1 organisms during 21-day exposure periods, which generally followed standard protocols. EE2 exposure at 62.5 to 1000 g/L reduced fecundity in brood 3 of F0; 1000 g/L reduced fecundity in both generations (brood 2 in F0; broods 1 and 2 in F1). However, broods 4 to 7 in F0, and broods 3 to 7 in F1 were not significantly affected, potentially indicating P450 induction and upregulation over time. Transgenerational studies were also performed with 20-hydroxyecdysone (ecdysone receptor agonist) and Testosterone (ecdysone receptor antagonist). Because these are known to act through the ecdysone receptor in D. magna, comparative responses of these invertebrate steroids and compounds that interact with vertebrate estrogen receptors (EE2, Faslodex) may provide information on mechanistic effects of select steroid pharmaceuticals in cladocerans.
Key words: ICI 182,780, ethynylestradiol, multigenerational, Daphnia magna
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