Ultrastructural changes induced by benzo[a]pyrene in sea bass (Dicentrarchus labrax) liver and intestine: importance of the intoxication route.

The ultrastructural effects of benzo[a]pyrene (BaP) on sea bass (Dicentrarchus labrax) liver and intestine were studied after experimental intoxication by two different routes: intraperitoneal injection and force-feeding. In both hepatocytes and enterocytes, the main structural perturbations concerned a large development of both rough and smooth endoplasmic reticulum and a great increase in the number of vacuoles and lysosomes in BaP-treated fish. After 17 days of contamination, some nuclear changes were observed, indicating the high reactivity of BaP metabolites which form covalent adducts with DNA and the long-term toxicity of this compound. However, in the intestine, after force-feeding intoxication, more perturbations were seen, particularly concerning the mitochondria. Both organs were altered in a different way with respect to the intoxication route. In BaP intraperitoneal injected fish, the liver was the first injured organ and presented heavier injuries than intestine. In force-feeding treated fish, the intestinal epithelium was the first concerned tissue and it was highly modified after BaP intoxication. The importance of the intoxication pathway in the effects of BaP on liver and intestine was discussed with special reference to their role in BaP uptake, metabolism, and distribution in the organism.