Estimation of Estrogenic and Antiestrogenic Activities of Selected Pesticides by MCF-7 Cell Proliferation Assay

Estrogenic activities of 20 selected pesticides—which are used for agricultural production as insecticides, fungicides and herbicides—were examined by estrogen receptor (ER)-dependent MCF-7 cell proliferation assay. Among them, chlordecone, dicofol, methoxychlor, -HCH, fenarimol, EPN, triadimefon, and triadimenol had estrogenic activities, all of which were suppressed by the addition of pure antiestrogen ICI 182,780. The first 5 compounds exhibited binding capacities to ER. The antiestrogenic activity of a compound was examined by estimating its suppressive effect on cell proliferation induced by 30 pM 17-estradiol. Strongly suspected antiestrogens were captan and myclobutanil, both of which were found to have the capacity to bind to ER and which might exert their activities by competing at the level of ER. Antiestrogenic activities of nitrofen, fenitrothion, fenarimol and triadimefon were also suggested. Affinities of the compounds for ER and/or androgen receptor (AR) were lower than those of synthetic estrogen (diethylstilbestrol) and testosterone (mibolerone), respectively. Fenitrothion had the highest affinity to AR. Chlordecone, dicofol, methoxychlor, nitrofen, fenarimol, myclobutanil and pyridate had capacities to bind both ER and AR. Chlordecone and pyridate were much more effective as competitors of estrogen binding to ER than androgen binding to AR and, conversely, nitrofen was a more effective competitor of androgen binding to AR.