Oxidative Stress Biomarkers and Antioxidant Enzymes in Liver and White Muscle of Nile Tilapia, Oreochromis niloticus, Exposed to an Endocrine Disruptor, Triclosan.

Both target and nontarget aquatic creatures have been observed to suffer negative impacts from pharmaceutical residues and metabolites. This study is aimed at evaluating the toxic effects of triclosan (TCS). The sublethal effects of TCS at concentrations 0.146 ppm (1/15), 0.219 ppm (1/10), and 0.438 ppm (1/5) on biochemical responses and oxidative stress biomarkers in the serum, liver, and muscle tissue of freshwater fish Nile tilapia, Oreochromis niloticus, were investigated for 15, 30, and 45 days. Levels of some serum biochemical parameters including protein and glucose reduced while glutamic oxaloacetic transaminase and glutamic pyruvic transaminase raised as concentration of TCS increased. The reactions of superoxide dismutase and glutathione-S-transferase and reduced glutathione were elevated, and the activities of reduced glutathione were reduced in fish liver and muscle. Malate dehydrogenase activity gradually rose, showing a metabolic response to stress, but NADH dehydrogenase activity gradually decreased, indicating mitochondrial malfunction. Chronic exposure to TCS below the lethal threshold can alter O. niloticus serum biochemical indexes and cause oxidative stress. This suggests that the drug exposure and its metabolites should be closely monitored in aquatic environments due to the potential harm they could do, even to organisms that are not the intended target.