US EPA

1249821 

Journal Article 

Antiandrogenic activity of phthalate mixtures: validity of concentration addition 

Christen, V; Crettaz, P; Oberli-Schrämmli, A; Fent, K 

2012 

1 

Toxicology and Applied Pharmacology
ISSN: 0041-008X
EISSN: 1096-0333 

259 

2 

169-176 

English 

22245847 

10.1016/j.taap.2011.12.021 

WOS:000301329800004 

http://www.sciencedirect.com/science/article/pii/S0041008X11004856
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Phthalates and bisphenol A have very widespread use leading to significant exposure of humans. They are suspected to interfere with the endocrine system, including the androgen, estrogen and the thyroid hormone system. Here we analyzed the antiandrogenic activity of six binary, and one ternary mixture of phthalates exhibiting complete antiandrogenic dose-response curves, and binary mixtures of phthalates and bisphenol A at equi-effective concentrations of EC(10), EC(25) and EC(50) in MDA-kb2 cells. Mixture activity followed the concentration addition (CA) model with a tendency to synergism at high and antagonism at low concentrations. Isoboles and the toxic unit approach (TUA) confirmed the additive to synergistic activity of the binary mixtures BBP+DBP, DBP+DEP and DEP+BPA at high concentrations. Both methods indicate a tendency to antagonism for the EC(10) mixtures BBP+DBP, BBP+DEP and DBP+DEP, and the EC(25) mixture of DBP+BPA. A ternary mixture revealed synergism at the EC(50), and weak antagonistic activity at the EC(25) level by the TUA. A mixture of five phthalates representing a human urine composition and reflecting exposure to corresponding parent compounds showed no antiandrogenic activity. Our study demonstrates that CA is an appropriate concept to account for mixture effects of antiandrogenic phthalates and bisphenol A. The interaction indicates a departure from additivity to antagonism at low concentrations, probably due to interaction with the androgen receptor and/or cofactors. This study emphasizes that a risk assessment of phthalates should account for mixture effects by applying the CA concept. 

Phthalates; Benzylbutylphthalate (BBP); Dibutyl phthalate (DBP); Diethylphthalate (DEP); Dimethyl phthalate (DMP); Di-2-ethylhexyl phthalate (DEHP); Bisphenol A; Mixture activity; Antiandrogenicity; Concentration addition; Toxic unit approach; Isobole method