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 interact with three major teleost steroid-binding sites was evaluated. Representative alkylphenols and phthalates, the pesticides dieldrin and toxaphene, the mycoestrogen zearalenone and the phytoestrogen genistein were tested for their ability to displace native ligand from putative estradiol receptor (ER), testosterone receptor (TR) and cortisol receptor (CR) from rainbow trout liver and brain. The ER displayed a higher affinity for alkylphenols than for phthalates, but both groups of compounds were 104-2.105 times less potent than estradiol in displacing specifically bound [3H]estradiol. The displacement of bound [3H]estradiol did not increase when these compounds were tested in combination. Toxaphene and dieldrin did not bind to the trout ER, either alone or in combination. Zearalenone and genistein were about 103-fold less potent than estradiol in displacing specifically bound [3H]estradiol from the trout ER and showed no increase in potency when tested in combination. None of the compounds tested showed evidence of binding to the TR or the CR, failing to displace specifically bound [3H]testosterone and [3H]cortisol respectively. It is concluded that the compounds tested are exclusively estrogenic in rainbow trout, albeit weakly so, and do not display any synergistic effects.