PCBs, liver lesions, and biomarker responses in adult walleye (Stizostedium vitreum vitreum) collected from Green Bay, Wisconsin

Adult walleye were collected from several locations in the Lower Fox River and Green Bay, Wisconsin (the assessment area) and two relatively uncontami nated reference locations (Lake Winnebago and Fatten Lake, Wisconsin) betwe en July and October in 1996 and 1997 Whole body and liver samples collected in 1996 were analyzed for total PCBs, PCB congeners, and liver histologica l lesions. Follow-up sampling in 1997 included examination of liver histopa thology, PCBs in liver samples, measurement of ethoxyresorufin-O-deethylase (EROD) activity, immunological evaluation of kidney and blood samples, mea surement of plasma vitellogenin, and examination of tissues for parasites a s well as bacterial and viral infections. Mean PCB concentrations in whole body and liver samples were elevated in assessment area walleye (4.6 to 8.6 and 3.6 to 6.4 mg/kg wet weight, respectively) compared to PCB concentrati ons in reference areas (0.04 mg/kg in walleye fillets from Lake Winnebago). A significant (p < 0.01) elevation was observed in the prevalence (26%) of hepatic preneoplastic foci of cellular alteration (FCA) and neoplasms in 5 to 8 year old walleye collected from the assessment area, compared to refe rence area fish (6% prevalence). Walleye from the assessment area also cont ained multiple FCA and hepatic tumors per liver sample, whereas no tumors a nd a reduced prevalence of FCA were observed in reference area walleye. Bot h tumors and FCA were more prevalent in female fish than in male fish withi n the 5 to 8 year age classes. There were no remarkable effects on immunolo gical parameters in assessment area walleye, although hematocrit was elevat ed and blood monocyte counts were 40% lower than those of reference area fi sh. The data did not show any clear distinctions in the prevalence of disea se between reference and assessment area walleye. EROD activity was similar in assessment area and reference area walleye. Plasma vitellogenin was ele vated in female walleye from eastern. Green Bay, but was not detected in ma le fish from this location. The results of this investigation demonstrate s ignificant elevation in hepatic preneoplastic lesions and hepatocellular ad enomas and carcinomas in assessment area walleye exposed to elevated concen trations of PCBs. These histopathological lesions are consistent with long- term exposure to tumor promoters such as PCBs, although quantitative associ ation between tumors and PCBs was not observed at the level of the individu al fish. Additional research would be needed to elucidate the causal mechan isms underlying tumorigenesis.