Effect of titanium dioxide nanoparticles on enzymatic antioxidants in gill tissue of Oreochromis niloticus

In this research, it was investigated the alterations in activities of some antioxidant enzymes of gill chosen as the target tissue in Oreochromis niloticus in response to titanium dioxide nanoparticles (TiO2-Np). For this purpose fish were exposed to 1.0 and 5.0 mg/L TiO2-Np for 4 and 14 days and catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione -S-transferase (GST) and glutathione reductase (GR) activities were determined. The significant changes in all analyzed antioxidant enzymes were observed due to medium concentration and exposure period in the exposure of TiO2-Np. CAT activity decreased in the exposure of 1.0 mg/L TiO2-Np after both periods (P˂0.05). In the higher concentration of TiO2-Np, CAT activity declined at 4 days, whereas it increased at 14 days (P˂0.05). SOD activity decreased in all the tested concentrations of TiO2-Np at 4 days (P˂0.05), while it was not observed a significant change in its activity at 14 days (P˃0.05). In 5.0 mg/L TiO2-Np exposed fish, although GPX activity declined at 4 days (P<0.05), it elevated at the end of the exposure period (P<0.05). In response to TiO2-Np exposure, GST activity showed an increase in its lower medium concentration after 4 days and in its higher medium concentration after both periods (P<0.05). It was determined a significant elevation in GR activity in exposure of 5.0 mg/L TiO2-Np after 4 and 14 days (P<0.05). In conclusion, our study indicated that all analyzed antioxidant enzymes in gill of O. niloticus were affected by TiO2-Np and that observed decreases or increases in enzyme activities of generally were higher in the exposure of 5.0 mg/L TiO2-Np.