No abstract

Male white sucker (Catostomus commersoni) from a population exposed to effluent from a bleached kraft mill and from a reference site were held in effluent or clean water for 4 d. To investigate bioavailable bioactive compounds, hepatic tissues were extracted and fractionated according to octanol−water partition coefficient (K ow) using reverse phase HPLC. Fractions were tested in vitro for the presence of compounds functioning as ligands for (i) the aryl hydrocarbon receptor (AhR) using mixed function oxygenase (MFO) induction in H4IIE cells, (ii) the estrogen receptor (ER) isolated from rainbow trout (Oncorhynchus mykiss) liver, (iii) the androgen receptor (AR) isolated from goldfish (Carassius auratus) testes, and (iv) sex steroid binding protein (SSBP) isolated from goldfish plasma. Polychlorinated dioxins and furans accounted for MFO activity of liver contaminants of log K ow > 5 but multiple nondioxin AhR ligands of log K ow 2 to 5 also caused significant induction. Compounds of log K ow 2 to 5 in livers of exposed fish exhibited significant competition for the AR, ER, and SSBP, indicating potential effects on hormone signaling and transport. The absence of most ligands for the AhR and sex steroid receptors in tissues of preexposed fish held in clean water demonstrates clearance of these compounds after short-term removal from effluent. This study demonstrates the utility of using wild fish tissue burdens to study the lipophilicities and the pharmacokinetic properties of bioavailable compounds functioning as ligands for the AhR and sex steroid hormone receptors.

Abstract-Androgen receptors (ARs) from fish were characterized in order to evaluate differences in the binding affinities of steroids and environmental chemicals between mammals and fish, among species of fish, and among target tissues within a species of fish. High-affinity, low-capacity ARs were identified in cytosolic fractions of rainbow trout brains (Oncorhynchus mykiss) and the brains, ovaries, and testes of goldfish (Carassius auratus) using [ 3 H]testosterone. The binding specificities of endogenous steroids to the ARs did not differ between goldfish tissues but did differ between goldfish and rainbow trout. Interspecies differences in binding specificities were also seen using cyproterone acetate, which bound to the ARs in the goldfish tissues, but not in the rainbow trout brains. The mammalian antiandrogens flutamide, vinclozolin and its metabolites 2-(((3,5)-dichlorophenyl-carbamoyl)oxy)-2-methyl-3-butenoic acid and 3Ј,5Ј-dichloro-2-hydroxy-2-methylbut-3-enanilide, along with procymidone did not bind to the ARs in any of the fish tissues tested. However, other mammalian antiandrogens including methoxychlor and its metabolite 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane, o,pЈ-DDT, o,pЈ-dichlorodiphenyldichloroethylene (DDE) and p,pЈ-DDE did bind to the fish ARs, but only in the goldfish testes, demonstrating tissue differences in AR binding specificities of environmental chemicals. These results may be due to the presence of multiple AR isoforms in the different fish species and tissues. This study supports the growing evidence of species differences in the potency and actions of endocrine-disrupting chemicals and suggests that multiple species need to be tested when screening the receptor binding ability of potential endocrine-disrupting chemicals.