IDENTIFICATION OF THE LAMPRICIDE 3-TRIFLUOROMETHYL-4-NITROPHENOL AS AN AGONIST FOR THE RAINBOW-TROUT ESTROGEN-RECEPTOR

Lampricide formulations containing 3-trifluoromethyl-4-nitrophenol (TF M) have been associated with induction of hepatic mixed function oxyge nase (MFO) activity and altered levels of circulating steroids in fish . Bioassay-directed chemical fractionations have shown MFO induction t o be associated with impurities in TFM field formulations. A similar t oxicity identification/ evaluation approach coupled to competitive bin ding to rainbow trout estro en receptors (ER) was used to identify com pounds associated with estrogenic responses in fish. In contrast to MF O induction, nearly all binding to the ER was associated with fraction s containing TFM, TFM isomers, and p-chlorophenol, p-Chlorophenol did not show any affinity for the receptor when tested separately. Dipheny l ether impurities identified in the fractions causing MFO induction a s well as analogues to dibenzo-p-dioxins suspected in these fractions also showed no affinity for the receptor when tested individually. Rel ative to estradiol, TFM demonstrated an affinity of 5.03 x 10(-5), com pared to 2.47 x 10(-4) for p-nonylphenol, a reported estradiol agonist . Vitellogenin induction in primary cultures of rainbow trout hepatocy tes indicated that TFM acts as an estradiol agonist.