title: Daphnia magna responses to a vertebrate estrogen receptor agonist and an antagonist: a multigenerational study.
abstract: Whereas ecological risk assessments rely on standardized aquatic toxicity tests to assess ecological hazards, these techniques have limited utility for endocrine-active compounds, including select pharmaceuticals. Due to structural similarity between of vertebrate estrogens and ecdysone, previous studies suggest that endocrine-active pharmaceuticals may interfere with invertebrate endocrine systems, while other investigations do not support these suggestions. We assessed effects of the pharmaceuticals 17alpha-ethinylestradiol and faslodex, model therapeutics designed to interact with vertebrate estrogen receptors, on endocrine biomarkers and transgenerational life-history parameters of a model invertebrate, Daphnia magna. Identical studies were performed with 20-hydroxyecdysone and testosterone, which served as positive controls for ecdysteroid receptor agonism and antagonism, respectively. Results from this study at biochemical, individual and population levels suggest that a mammalian estrogen receptor agonist and antagonist did not act through the ecdysone receptor in D. magna. Acute-to-chronic ratios based on various chronic responses ranged from 2.59 to 5.18 for 17alpha-ethinylestradiol and 1.29-12.9 for faslodex. Toxicity exerted by these therapeutics on D. magna likely resulted from non-endocrine-mediated responses. Mechanism-specific biomarkers, multigenerational designs and population growth models may be useful to assess organismal and population level responses to low-level exposures, which may serve to reduce uncertainty in future hazard assessments of invertebrate responses to endocrine-active pharmaceuticals in the environment.
authors: Department of Environmental Studies, One Bear Place #97266, Baylor University, Waco, TX 76798, USA.
authors: Rebekah L
authors: RL
authors: Clubbs
authors: Bryan W
authors: BW
authors: Brooks
mesh_terms: D000818:Animals; D001681:Biological Assay; D003621:Daphnia / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004441:Ecdysterone / Q000633:toxicity; D004703:Endocrine System / Q000187:drug effects* / Q000378:metabolism; D004997:Ethinyl Estradiol / Q000633:toxicity; D011158:Population Growth; D011960:Receptors, Estrogen / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012098:Reproduction / Q000187:drug effects / Q000502:physiology; D018570:Risk Assessment; D013739:Testosterone / Q000633:toxicity; D018675:Toxicity Tests; D014714:Vertebrates; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D011960:Receptors, Estrogen; D014874:Water Pollutants, Chemical; D013739:Testosterone; D004997:Ethinyl Estradiol; D004441:Ecdysterone