Interactive effects of cadmium and benzo(a)pyrene on cellular structure and biotransformation enzymes of the liver of the European eel Anguilla anguilla

Abstract

Interactive effects of cadmium and benzo(a)pyrene (BaP) on eel Anguilla anguilla liver were studied at the ultrastructural and biotransformation enzyme levels. Seawater-adapted eels were held for 24 days in either clean or cadmium-containing (5 μg Cd −1) seawater. then given a single intraperitoneal injection of BaP (20 mg kg −1 body weight) and finally sacrificed 24 h later. Cadmium exposure alone caused a hepatic perivascular fibrosis. whereas the short-term BaP intoxication alone produced marked lipid droplet accumulation associated with glycogen depletion. When eels were exposed to both toxicants together, the liver showed a complete disorganisation of the hepatic parenchyma including nuclear degeneration. The existence of elements of a biotransformation enzyme system, i.e. cytochrome P-450 monooxygenase system and glutathione-S-transferase (GST). was demonstrated in the liver. BaP injection alone had no detectable effect on microsomal cytochrome P-450 content and NADPH-cytochrome c reductase activity but markedly increased 7-ethoxyresorufin O-deethylase (EROD) and benzo(a)pyrene hydroxylase (BaPMO) activities (induction factors of 15- and 35-fold, respectively). In contrast, cytosolic GST activity was slightly decreased by this treatment. In cadmium-exposed eels, BaP treatment elicited a higher increase in EROD and BaPMO activities (induction factors of 19- and 71-fold. respectively) and also causes a 1.8-fold increase in cylochrome P-450 microsomal content. The effects of cadmium on biotransformation enzymes are discussed in relation to the ultrastructural effects of both toxicants.