Characteristics of ligands for the Ah receptor and sex steroid receptors in hepatic tissues of fish exposed to bleached kraft mill effluent

Male white sucker (Catostomus commersoni) from a population exposed to effl uent from a bleached kraft mill a nd from a reference site were held in eff luent or clean water for 4 d. To investigate bioavailable bioactive compoun ds, hepatic tissues were extracted and fractionated according to octanol-wa ter partition coefficient (K-OW) using reverse phase HPLC. Fractions were t ested in vitro for the presence of compounds functioning as ligands for (i) the aryl hydrocarbon receptor (AhR) using mixed function oxygenase (MFO) i nduction in H411E cells, (ii) the estrogen receptor (ER) isolated from rain bow trout (Oncorhynchus mykiss) liver, (iii) the androgen receptor (AR) iso lated from goldfish (Carassius auratus) testes, and (iv) sex steroid bindin g protein (SSBP) isolated from goldfish plasma, Polychlorinated dioxins and furans accounted for MFO activity of liver contaminants of log K-OW > 5 bu t 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 exhibite d significant competition for the AR, ER, and SSBP, indicating potential ef fects on hormone signaling and transport. The absence of most ligands for t he AhR and sex steroid receptors in tissues of preexposed fish held in clea n 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.