Biochemical and (ultra)structural hepatic perturbations of Brachydanio rerio (Teleostei, Cyprinidae) exposed to two sublethal concentrations of copper sulfate.

The aim of this study was to compare biochemical and (ultra)structural perturbations induced by Cu in the liver of Brachydanio rerio exposed for 14 days to sublethal concentrations of copper and then replaced for 14 days to clean water. Toxicity of Cu was clearly demonstrated: simultaneously to Cu accumulation, the liver developed large lysed areas and hepatocytic alterations. However, the majority of the parenchyma was composed of functional dark hepatocytes displaying typical feature of increased metabolism: development of rough reticulum, increase in size of nucleus and nucleolus, glycogenic depletion. Increase in hepatic protein content and of anti-oxidative defences (glutathione content, catalase and glutathione-S-transferase (GST) activities) indicated that the overall response of the liver was adaptative. In all hepatocytes a cord-like structure of the nucleoli was suspected to be associated to metal deposition. After 14 days depuration, the liver still contained high Cu concentrations and the hepatic alterations were not reversed. Such complementary studies are necessary for a better understanding of the deleterious effects of pollutants and for the development of biomarkers for metal toxicity.