BINDING OF XENOBIOTICS TO THE ESTROGEN-RECEPTOR OF SPOTTED SEA-TROUT - A SCREENING ASSAY FOR POTENTIAL ESTROGENIC EFFECTS

Several xenobiotics that bind to mammalian estrogen receptors (ER) were tested for their ability to bind to the hepatic ER of a marine fish, the spotted seatrout (Cynoscion nebulosus). Incubation of cytosolic extracts with the antiestrogens clomiphene, tamoxifen, and nafoxidine caused displacement of H-3-estradiol from its receptor. Kepone (chlordecone) also bound to seatrout ER, but it had a lower affinity than that observed with mammalian ER. Preliminary results indicated that these compounds have antiestrogenic or estrogenic actions in the spotted seatrout. However, several DDT derivatives and PCB mixtures failed to displace estradiol from the spotted seatrout ER, even though they have been shown to bind to mammalian ER. The lack of binding to spotted seatrout ER by several of the xenobiotics may be due to structural differences between ER in spotted seatrout and in mammals. These results indicate that the spotted seatrout ER assay can be used for screening xenobiotics for possible estrogenic activity in teleosts.