HEPATIC MIXED-FUNCTION OXIDASES INDUCED IN POPULATIONS OF WHITE SUCKER, CATOSTOMUS-COMMERSONI, FROM AREAS OF LAKE-SUPERIOR AND THE ST-MARYS RIVER

Mixed function oxidases (MFO) are a family of inducible enzymes which oxygenate natural and synthetic chemicals alike, making them amenable to conjugation and excretion. The utility of MFO induction in white suckers as an indicator of chemical contamination was examined in three "areas of concern," Jackfish Bay, St. Marys River, and the Kaministiquia River. MFO determinations in spawning suckers suggested no induction, although white suckers captured in the summer from Jackfish Bay had MFO levels up to 6 (2,5-diphenyloxazole metabolism) and 7 (Benzo-a-pyrene hydroxylase) fold higher than did reference suckers. Similar induction was found in suckers collected in the summer from the Kaministiquia River and from the St. Marys River, hepatic MFO activities 3 (PPO) and 5 (BaP) times those of the reference populations suggesting exposure to chemicals with MFO inducing potential. The relative induction of hepatic MFO at all three polluted locations is a sensitive measure of industrially discharged xenobiotics, which might be useful in monitoring the efficiency of remedial action plans.