title: Incorporation of S-9 activation into an ER-alpha transactivation assay.
abstract: We evaluated the feasibility of incorporating an exogenous metabolic activating system into an estrogen receptor-alpha transactivation assay. 17beta-estradiol (E2), and the proestrogenic pesticide methoxychlor (MXC) were evaluated for activity in the presence and absence of Aroclor-1254 induced rat liver S-9 fractions. Both E2 and MXC responded consistently in the assay with average EC(50) values of 9.6 x 10(-11) M and 1.2 x 10(-5) M, respectively. In the presence of a 0.1% S-9 fraction, the EC(50) for E2 was increased to 1.4 x 10(-9) M and that for MXC decreased to 4.9 x 10(-7) M, with both compounds demonstrating increased secondary metabolite formation as evidenced by HPLC analysis. Consistent with these data, metabolites of E2 and MXC exhibited decreased and increased potencies, respectively, in the assay system relative to the parent molecules. S-9 was compatible with the MCF-7 reporter assay and has the potential to enhance detection of proestrogenic materials.
authors.affiliation: Toxicology and Environmental Research and Consulting, The Dow Chemical Company, 1803 Building, Midland, MI 48764, USA. gdcharles@dow.com
authors.forename: G D
authors.initials: GD
authors.lastname: Charles
authors.forename: M J
authors.initials: MJ
authors.lastname: Bartels
authors.forename: C
authors.initials: C
authors.lastname: Gennings
authors.forename: T R
authors.initials: TR
authors.lastname: Zacharewski
authors.forename: N L
authors.initials: NL
authors.lastname: Freshour
authors.forename: B
authors.initials: B
authors.lastname: Bhaskar Gollapudi
authors.forename: E W
authors.initials: EW
authors.lastname: Carney
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods*; D020111:Chlorodiphenyl (54% Chlorine) / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D017930:Genes, Reporter / Q000187:drug effects; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008297:Male; D008731:Methoxychlor / Q000494:pharmacology; D008862:Microsomes, Liver / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D047628:Estrogen Receptor alpha; D011960:Receptors, Estrogen; D020111:Chlorodiphenyl (54% Chlorine); D004958:Estradiol; D008156:Luciferases; D001616:beta-Galactosidase; D008731:Methoxychlor