A yeast assay based on the gilthead sea bream (teleost fish) estrogen receptor β 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) beta a estrogen receptor (sbER beta a) and substances known to have estrogenic activity. 17 beta-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 sbER beta a and sbER alpha revealed that sbER beta a binds E-2 with 6.5-fold higher affinity than sbER alpha, 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 E-2 in sbER alpha than sbER beta a, 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. (C) 2009 Elsevier Inc. All rights reserved.