PARENT SESSION
PT2 - Endocrine Disruption
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P580) Screening for androgen and glucorticoid receptor (ant)agonists using MDA-kb2 cells.

Murphy, Margaret^*,1,2,3, Villeneuve, Daniel^2,3, Lam, W², Jones, Paul^2,3, Giesy, John^1,2,3, 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