title: Assessment of interactions of diverse ternary mixtures in an estrogen receptor-alpha reporter assay.
abstract: This study used an MCF-7 cell based ER-alpha reporter gene assay to assess chemical interactions within the following ternary mixtures: (1) three synthetic pesticides, methoxychlor (MXC), o,p-DDT, and dieldrin; (2) three polyaromatic hydrocarbons, benzo[a]pyrene (BAP), 1,2-benzanthracene (BENZ), and chrysene (CHRY); and (3) an endogenous estrogen, [17beta-estradiol, (E(2))]; a phytoestrogen, genistein (GEN); and a synthetic estrogen, o,p-DDT. A full factorial design in which four concentrations of each chemical were assessed in all possible combinations (64 treatment groups) was utilized. In addition, mixtures were tested in both a low range (concentrations near the individual chemical response thresholds) and a high range ( approximately 2-10x higher) experiment. A response surface was estimated using a nonlinear mixed model, and the cumulative response in each mixture was evaluated for departure from additivity. The mixture of E(2), GEN, and DDT exhibited antagonistic interactions (p < 0.001) in both concentration ranges. However, specific interactions between E(2)/GEN and E(2)/DDT differed between the low and high range concentrations. The BAP/BENZ/CHRY mixture did not depart significantly from additivity (p = 0.66) in either concentration range, although response levels were generally low. The MXC/DDT/dieldrin mixture did not depart significantly from additivity in either the high (p = 0.065), or low dose range (p = 0.506), with generally minimal responses dominated by MXC and DDT. This methodology has allowed for a rigorous statistical evaluation of potential departures from additive interactions in endocrine active mixtures. In no case was a significantly greater-than-additive (synergistic) interaction observed.
authors.affiliation: Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan 48674, USA.
authors.forename: Grantley D
authors.initials: GD
authors.lastname: Charles
authors.forename: C
authors.initials: C
authors.lastname: Gennings
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Zacharewski
authors.forename: B Bhaskar
authors.initials: BB
authors.lastname: Gollapudi
authors.forename: Edward W
authors.initials: EW
authors.lastname: Carney
mesh_terms: D001681:Biological Assay; D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D047628:Estrogen Receptor alpha; D004967:Estrogens / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D008954:Models, Biological; D010575:Pesticides / Q000378:metabolism / Q000494:pharmacology; D011084:Polycyclic Aromatic Hydrocarbons / Q000378:metabolism / Q000494:pharmacology; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D015262:Xenobiotics / Q000378:metabolism* / Q000494:pharmacology; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
chemical_list: D047628:Estrogen Receptor alpha; D004967:Estrogens; D010575:Pesticides; D011084:Polycyclic Aromatic Hydrocarbons; D011960:Receptors, Estrogen; D015262:Xenobiotics; D008156:Luciferases; D001616:beta-Galactosidase