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COMPARISON OF FATHEAD MINNOW AND HUMAN ESTROGEN RECEPTOR BINDING TO ENDOCRINE DISRUPTING COMPOUNDS
Citation:
RIDER, C. V., P. C. HARTIG, M. C. CARDON, AND V. S. WILSON. COMPARISON OF FATHEAD MINNOW AND HUMAN ESTROGEN RECEPTOR BINDING TO ENDOCRINE DISRUPTING COMPOUNDS . Presented at SETAC, Montreal, QC, CANADA, November 05 - 09, 2006.
Description:
Environmental estrogens have the potential to disrupt endocrine function in a myriad of species. However, in vitro assays designed to detect and characterize endocrine disrupting chemicals (EDCs) typically utilize mammalian estrogen receptors. Our overall objective is to characterize the estrogen binding profile of estrogen receptors from a range of non-mammalian species including representative fish, amphibian, and reptile species. The affinity of compounds for these estrogen receptors is being determined in competitive whole cell binding assays using binding to recombinant human ER¥á as a basis for comparison. Test compounds were selected based on environmental relevance and reports of species specific endocrine effects and include: 17¥â-estradiol, estrone, ¥á-zearalanol, methoxychlor, bisphenol A, and atrazine. The current work consists of binding studies conducted with the fathead minnow ER¥á, which was isolated and sequenced from a cDNA library. Saturation binding experiments yielded dissociation constants (Kd) in the nanomolar range with fathead minnow ER¥á displaying a slightly higher Kd than human ER¥á. Functional characterization of the fathead minnow receptor revealed that it is temperature sensitive and has reduced ligand binding ability at higher temperatures (37¡ÆC), whereas, human ER¥á is temperature stable. Initial results from binding studies indicate that 17¥â-estradiol has comparable affinity for fathead minnow ER¢¯ and human ER¥á (IC50s of 5.1 nM ¡¾ 1.7 and 7.8 nM ¡¾ 0.6 17¥â-estradiol, respectively). This work tests the assumption that ER binding can be extrapolated across-species in endocrine disruption studies, as well as possibly identifying or confirming compounds with species specific estrogenicity. Funding was provided by the NCSU/EPA Cooperative Training Program CT826512010. Disclaimer: This is an abstract of a proposed presentation and does not necessarily reflect USEPA policy.