Toxicological effects of oxyfluorfen on oxidative stress enzymes in tilapia Oreochromis niloticus

Several environmental pollutants enhance the intracellular formation of reactive oxygen species, and can lead to the damage of macromolecules and a decrease in oxidant defences levels in fish. The effects of the herbicide oxyfluorfen on the activities of antioxidant enzymes such as catalase, superoxide dismutase, glutathione reductase, and glutathione S-transferase were evaluated in freshwater fish Oreochromis niloticus. These were determined in tilapia liver exposed to sublethal concentrations (0.3 and 0.6 mg/L at 7, 14, and 21 days of exposure. This study also analyzed the effects of oxyfluorfen on the total fatty acid profile. The results showed that CAT activity was higher in tilapia exposed to oxyfluorfen at the sampling days, except at the highest concentration after 21 days. Similarly, the enhancing effect of the herbicide was observed on the GR activity. However, its effect was moderate at the highest dose. On the contrary, fish treated with oxyfluorfen at both doses displayed a decrease in the SOD activity. After 7 days of treatment at both concentrations tilapia showed a significant increase in GST levels, although the enzymatic activity decreased at 14 and 21 days of exposition when compared with the control. The major saturated fatty acids measured in tilapia liver were the palmitic acid (C16:0; 17.9%) and stearic acid (C18:0; 8.7%). The exposure to oxyfluorfen caused a significant increase of the oleic acid (C18:1), whereas the amount of nervonic acid (C24:1) increased at all sampling data. The results of the present study should be taken in account when using tilapia as an environmental indicator species in studies of xenobiotic biotransformation and biomarker response, as well as in monitoring programmes.