Interaction of endocrine disrupting chemicals, singly and in combination, with estrogen-, androgen-, and corticosteroid-binding sites in rainbow trout (Oncorhynchus mykiss)

The ability of chemicals with known endocrine disrupting activity to intera ct with three major teleost steroid-binding sites was evaluated. Representa tive alkylphenols and phthalates, the pesticides dieldrin and toxaphene, th e mycoestrogen zearalenone and the phytoestrogen genistein were tested for their ability to displace native ligand from putative estradiol receptor (E R), testosterone receptor (TR) and cortisol receptor (CR) from rainbow trou t liver and brain. The ER displayed a higher affinity for alkylphenols than for phthalates, but both groups of compounds were 10(4)-2 x 10(5) times le ss potent than estradiol in displacing specifically bound [H-3]estradiol. T he displacement of bound [H-3]estradiol did not increase when these compoun ds were tested in combination. Toxaphene and dieldrin did not bind to the t rout ER, either alone or in combination. Zearalenone and genistein were abo ut 10(3)-fold less potent than estradiol in displacing specifically bound [ H-3]estradiol from the trout ER and showed no increase in potency when test ed in combination. None of the compounds tested showed evidence of binding to the TR or the CR, failing to displace specifically bound [H-3]testostero ne and [H-3]cortisol respectively. It is concluded that the compounds teste d are exclusively estrogenic in rainbow trout, albeit weakly so, and do not display any synergistic effects. (C) 1999 Elsevier Science B.V. All rights reserved.