Relationship between ultrastructural changes and EROD activities in liver of fish exposed to Benzo[a]pyrene

Laboratory experiments were carried out to investigate the relationship between hepatocytological changes and EROD activities in the demersal fish Solea ovata up to 7 days following intraperitoneal injection of 0.1, 0.5, 1, 5 and 10 mg/kg benzo[a]pyrene (B[a]P). At 1 and 5 mg/kg of B[a]P, observable cytological alterations involved increase in abundance of lipofuscin granules, peroxisomes, mitochondria, lipid droplets and lysosomes, slight proliferation of the ER system, and glycogen depletion. At a higher dose (10 mg/kg) of B[a]P, condensation of cytoplasmic content was observed. Stereological analysis also showed apparent changes in hepatic lipofuscin granules, peroxisomes, mitochondria and lipids in response to B[a]P exposure. Experimental results demonstrated a good dose-response relationship between exposure to B[a]P and changes in EROD activities. Numerical densities of hepatic lipofuscin granules and peroxisomes were significantly correlated with EROD activities (r=0.84, 0.75, respectively, P < 0.01). The possible relationship between EROD induction, increases of lipofuscin granules and peroxisomes as a result of B[a]P exposure in S. ovata is discussed. The observed link between EROD induction and hepatocytological changes in response to toxicant exposure provides a more meaningful interpretation of EROD induction in ecotoxicological studies.