Effects of Diclofenac on the Oxidative Stress Parameters of Freshwater Fish Oreochromis niloticus

The indiscriminate use and abuse of pharmaceuticals have led to pharmaceutical residues in the aquatic environment which has been receiving great attention since significant levels of contamination have been found. The present study investigated the acute and sub-lethal effects of a pharmaceutical drug diclofenac on oxidative stress parameters and the recovery ability in O. niloticus. The juveniles were exposed to different concentrations of diclofenac to determine the 96 h LC50. The results indicated that diclofenac was toxic to O. niloticus with a 96 h LC50 of 0.489mg/L. The percentage mortality increased as the concentrations increased.  Fish were exposed to a control (0.00 mg/L) and three sub-lethal concentrations of 0.48, 0.32, and 0.25 mg/L of diclofenac for 28 days and allowed to recover for 7 days. The result of the sub-lethal test indicated that the responses were dose and duration dependent. The oxidative stress results showed significant concentration- and time-dependent increases in the values of lipid peroxidation, glutathione peroxidase, glutathione reductase and reduced glutathione but reduction in catalase and superoxide dismutase in the liver of the exposed fish. Many of the oxidative parameters were found to be restored after the 7-day recovery period. These results showed that diclofenac exposure had a profound negative influence on the selected indices of O. niloticus.