No abstract

The Kalamazoo River Superfund site in Michigan is contaminated with polychlorinated biphenyls (PCBs), which were heavily discharged into the river from several paper companies as part of the deinking process in the 1950s through 1970s. We characterized biomarkers of chronic PCB exposure in a resident fish population using real-time reverse transcriptase-polymerase chain reaction to examine mRNA expression levels of multiple genes in carp (Cyprinus carpio) liver from PCB contaminated and reference sites in the Kalamazoo River. We also measured these same genes in juvenile carp exposed to dietary PCBs for 4 months. Kalamazoo River carp had significantly increased levels of cytochrome P450 1A (CYP1A) mRNA as did carp fed PCBs in the laboratory. No significant mRNA upregulation occurred in the specific oxidative stress genes (gamma-glutamylcysteine synthetase and magnesium superoxide dismutase) and metabolic genes (phosphoenolpyruvate carboxykinase and nucleolin) examined. These data are consistent with the idea that carp from the Kalamazoo River Superfund Site are responding to PCB exposure via upregulation of CYP1A independent of activation of the oxidative stress response genes normally thought to be co-regulated with CYP1A.

Cytochrome p450 1A (cyp1A), pigmented macrophage aggregate (PMA) variables and fish descriptive characteristics were measured in field-caught adult carp Cyprinus carpio from two upstream reference sites and two downstream Superfund sites contaminated with polychlorinated biphenyls (PCBs) in the Kalamazoo River, MI, U.S.A. Liver PCB content in fish differed among sites, and immunocytochemical cyp1A protein expression was significantly elevated in fish liver at contaminated sites and with liver PCBs. PMA number (number per mm 2 ), mean size [mean size (area) per mm 2 ] and percentage area occupied (total area of PMAs per total field area evaluated) were significantly greater in fish livers from the contaminated sites. PMA number was significantly greater at one contaminated site, Lake Allegan, than at the Trowbridge Dam impoundment, the other contaminated site. The level of cyp1A protein was significantly correlated with PMA mean size and PMA per cent area but not with PMA number. These results suggest that carp are responding to PCB contamination and point to complex site dynamics related to fish condition in the Kalamazoo River.