Article Biochemical and histopathological changes in liver of the Nile tilapia from Egyptian polluted lakes

The aim of the present study was to analyze the impact of environmental contamination on oxidative stress and histopathologic biomarkers in liverof theNile tilapia,Oreochromis niloticus, collected from four sites that differ in their extent of pollution load, including heavy metals: the southeast basin (SEB), main basin (MB), and northwest basin (NWB)of LakeMariut aswell as Boughaz El-Maadiya, a channel in Lake Edku. The SEBwas the less-impacted site, and thus considered as a reference. High concentrations of heavy metals (cadmium, copper, iron, lead, zinc, and manga-nese) were detected in fish liver at sites with anthropogenic pressure. All biomarkers, lipid peroxidation (in theMB, NWB, and Lake Edku), superoxide dismutase (in the MB and NWB), and glutathione peroxidase, and reduced glu-tathione (in theNWB)were found to be significantly higher compared to the reference values. Catalase, glutathione reductase, and glucose-6-phosphate dehydrogenase showed a varied response and displayed significantly lower activities in the polluted sites. Certain hepatic lesions, detected microscopically, were stimulated in fish from the MB andNWB, reflecting the high contamination of these areas. These included foci of necrosis, melanomacrophage infiltration, congestion, nuclear pyknosis, and extensive vacuolation corresponding to relatively higher lipid content. Overall, our results suggest that the selected biomarkers are useful for the assessment of pollution impacts in natural aquatic environments influenced bymultiple pollution sources. The existenceof chronic backgroundpollutionof the test sites implies that the observed biomarker responses cannot be solely attributed to heavy metals