POLYCHLORINATED-BIPHENYLS AND NAPHTHALENES - LONG-LASTING INDUCTION OF OXIDATIVE STRESS IN THE RAT

A single dose of polychlorinated biphenyls (PCBs; 100 mg/kg) or naphth alenes (PCNs; 20 mg/kg) was given i.p. to male Sprague-Dawley rats. Af ter 1, 3, 7 or 14 days or 3 months hepatic cytochrome P450 activities, lipid peroxidation status, vitamin A or E and glutathione (GSH) conte nt, and antioxidative enzyme activities were evaluated. PCBs and PCNs induced EROD (7-ethoxycoumarin O-deethylase) activity up to 50-fold an d the activity was still elevated after 3 months. Concomitantly to thi s P450 induction the lipid peroxidation level (conjugated dienes) incr eased 2-fold. PCBs decreased hepatic vitamin A and E content and both chemicals decreased catalase and superoxide dismutase activities. Gluc ose-6-phosphate dehydrogenase and GSH-S-transferase activities and GSH -content were increased, GSH-peroxidase activity was not affected. In conclusion, these halogenated aromatic hydrocarbons caused a long-last ing impairment in the antioxidative defence system and an increase in oxidative stress in rat liver. These effects are probably closely link ed with the ability of these chemicals to act as tumor promoters.