Effect of the induced drug-metabolizing enzyme activity on the duration of oxolinic acid in fish

One group of 60 carp (ca 100 g each) were fed with a diet containing polychlorinated biphenyl (PCB) (1 mg PCB/kg body weight/day) for 2 weeks to induce drug-metabolizing enzymes. A second group of 60 carp were fed a PCB-free diet as a control. After pretreatment, oxolinic acid (OA) was administered in feed to PCB-treated and control fish in a single dose of 20 mg OA/kg body weight. The peak concentrations of OA in the blood, liver and muscle of PCB-treated fish were lower than half of those in the control. Furthermore, the duration times of OA in the liver and blood of PCB-treated fish were also shortened compared with those in the control. In another test in vitro with hepatic microsomes, the produced amount of dihydroxy-OA in PCB-treated fish increased more than 30-fold compared with that in controls. These facts suggest that the induction of the drug-metabolizing enzyme activity by pollutants such as PCB, will result in large differences in the duration of drugs in fish, when the drugs accept enzymatic reactions.