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(P580) Screening for androgen and glucorticoid receptor (ant)agonists using MDA-kb2 cells.
Murphy, Margaret*,1,2,3, Villeneuve, Daniel2,3, Lam, W2, Jones, Paul2,3, Giesy, John1,2,3, 1 Zoology Department, Michigan State University, East Lansing, MI, USA2 National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI, USA3 Institute for Environmental Toxicology, Michigan State University, East Lansing`, MI, USA
ABSTRACT- MDA-kb2 cells are human breast carcinoma cells that were stably transfected with a luciferase reporter gene that can be activated by compounds acting through either the androgen receptor (AR) or glucocorticoid receptor (GR). The MDA-kb2 bioassay was developed by the U.S. Environmental Protection Agency as an in vitro assay for Tier-I screening of hormonally active compounds. In this study, the MDA-kb2 bioassay was used to screen over 50 xenobiotic chemicals, including polycyclic aromatic hydrocarbons, several pesticides, triazine herbicides and metabolites, organotins, polybrominated diphenyl ethers, perfluorooctanesulfonate, alkylphenols, non-coplanar polychlorinated biphenyls (PCB), and several pharmaceuticals for AR and GR (ant)agonist activity. Most of the compounds tested showed no hormonal activity in the MDA-kb2 assay. However, several compounds showed either significant agonist or antagonist activity. At a concentration of 8.4 g/L, benzo[a]pyrene induced a response equivalent to 20% of the maximum activity observed for a 600 pM testosterone (T) standard (%Tmax). PCB 138 (0.15-996 ng/ml) caused a dose-dependent decrease in activity, from 73%Tmax to 27%Tmax when co-exposed with 350 pM T. The MDA-kb2 assay was also used to screen sediment extracts that had shown both estrogen receptor and aryl hydrocarbon receptor-mediated activity in other assays. None of the sediment extracts tested elicited a significant response in the MDA-kb2 assay. The EC50 for T was 58 ± 8 pM with a detection limit around 8 ± 3 pM . The EC50 and detection limit for dihydrotestosterone was in the same range. The EC50 for GR mediated effects of corticosterone was in the 20-50 nM range. Overall, the MDA-kb2 assay appears to be a useful tool for screening both xenobiotics and environmental extracts for hormonally active or antagonistic compounds.
Key words: androgen receptor, antiandrogen, glucocorticoid receptor, endocrine screening
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