A yeast assay based on the gilthead sea bream (teleost fish) estrogen receptor beta for monitoring estrogen mimics.

A yeast (Saccharomyces cerevisiae)-based assay was developed and tested with steroids and chemicals (mostly pesticides). The induction of beta-galactosidase activity was strictly dependent on the presence of seabream (Sparus aurata) betaa estrogen receptor (sbERbetaa) and substances known to have estrogenic activity. 17beta-Estradiol (E(2)) and diethylstilbestrol (DES), both agonists, were most active and the antagonist tamoxifen (TAM) was 14-fold less active than E(2). Among the chemicals tested bisphenol-A was most active, followed by pentachlorophenol and naphthalene. Ligand-binding assays with recombinant sbERbetaa and sbERalpha revealed that sbERbetaa binds E(2) with 6.5-fold higher affinity than sbERalpha, confirming the selection of a high sensitive receptor for the yeast assay. DES, ICI 182,780, estrone and TAM had higher relative binding affinity to E2 in sbERalpha than sbERbetaa, although there was no difference in IC50 for these steroids between the two receptors. These results reveal the usefulness of using the yeast-based receptor assay for detecting chemical interaction with steroid receptors from contaminated samples.