Isolation of MFO inducers from tissues of white suckers caged in bleached kraft mill effluent

White sucker (Catostomus commersoni) caged for 3 days in a breached kraft m ill effluent (BKME) stream had elevated mixed function oxygenase (MFO) acti vities 15-90 fold those of fish caged in a reference stream. Liver composit es of male and female fish were ground and extracted with dichloromethane ( DCM), methanol or 50% DCM/ methanol, and tested for MFO activity in rat hep atoma cells (H4IIE). There was no difference in the potency of H4IIE EROD i nduction among the three solvents, so DCM extracts were sprit into 31 fract ions using reverse phase high pressure liquid chromatography (HPLC). H4IIE MFO activity was elevated in several fractions, with three early peaks and several later peaks of induction, indicating several classes or compounds c ausing MFO induction were present in the fish livers. Polychlorinated diben zo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and chlorinated diphenylethers (CDPEs) were detected in several late-eluting fractions, bu t concentrations were not high enough for these compounds to be solely resp onsible for the observed induction. Induction by liver extracts decreased a s cell exposure times increased (24, 48 or 72 h), suggesting that some indu cers were more easily metabolized and eliminated from the H4IIE cells. In c ontrast, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2378-TCDD) had similar potenc y over 24, 48 and 72 h, as it was relatively resistant to metabolism. (C) 2 000 Elsevier Science Ltd. All rights reserved.