Relation of hepatic microsomal monooxygenase activity to tissue PCBs in rainbow trout (salmo gairdneri) injected with [14C] PCBs

Abstract

The relationship of tissue PCB levels to hepatic microsomal monooxygenase activity in rainbow trout (Salmo gairdneri) was assessed. This was accomplished by injecting individual trout with corn oil vehicle or with a [14C]PCB mixture in corn oil. At 3 to 70 d after injection, tissue [14C]PCB concentrations were determined by scintillation counting of solubilized tissue samples, and hepatic microsomes were prepared and assayed for ethoxyresorufin-O-deethylase and ethoxy-coumarin-O-deethylase activities. At three days after injection only the highest doses of PCBs caused elevation of hepatic microsomal monooxygenase activity. At later times, muscle and liver concentrations of PCBs at or lower than 250 ng/g were associated with hepatic microsomal monooxygenase activity at or near control levels. Elevated hepatic microsomal monooxygenase activity was associated with muscle and liver PCB concentrations 300 ng/g or higher, but not all fish with tissue PCBs above this concentration had elevated hepatic microsomal monooxygenase activity.