Effects of copper on Xenopus laevis liver

Copper is an essential element to living organisms for which it is involved as a co-factor in multiple physiological processes included carbohydrate and lipid metabolism, red blood cell formation and iron absorption and transport1. However, at high concentrations this metal is toxic because induces reactive oxygen species formation (ROS) that lead to oxidative stress and so cause damage to biological structures2. In this study, we evaluated the effects of copper on liver of Xenopus laevis after three weeks of exposure at 1mg/L of CuCl, the maximum concentration accepted for human use (ARPA, DPR236/88). X. laevis, like amphibian is directly exposed to the aquatic environment and sensitive to pollutants. For this reason, X. laevis is an important biomarker and so as a good model organism for ecotoxicological studies3. The effects of copper were analysed at light microscope on the livers of control and treated frogs and by Hematoxylin- Eosin and Mallory stainings to study the general histology, and by PAS and Perls stainings to evaluate the changes on glycogen metabolism and increase of hemosiderin presence, the iron storage complex, respectively. The tissue of treated livers showed evident damages and an increase in size and number of melanomacrophages, a clear indirect marker of inflammation and degenerative processes4. Instead, by Real-time PCR, we detected also mRNA expression levels of ATP7B, an important copper-transporting that appeared down-regulated in the treated frogs. We revealed that this decrease was also for the specific protein by Western Blotting and confirmed by immunohistochemistry technique using a polyclonal antibody anti-ATP7B. In conclusion, the data are indicative that a continuous exposition at 1mg/L of CuCl, a low concentration, damages the X. laevis liver suggesting the need for further experiments to elucidate better the toxicity of this metal and its environmental impact and on human health.