Glutathione Related Enzyme Levels of Freshwater Fish as Bioindicators of Pollution

The livers and kidneys of freshwater fish species, Oreochromis niloticus and Clarias lazera, collected from sewage polluted sites (Ismailia and El-Bahr El-Azam) and industrial polluted sites (Shubra and El-Tebin) of Nile River were analyzed for different antioxidant defense enzymes. The liver and kidney glutathione transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx) were higher in O. niloticus captured from all the polluted areas compared to the control. Low GST activities were found in 33.3%, 60% and 53% in the livers and 100%, 80% and 53% in the kidneys of C. lazera captured from El-Bahr El-Azam, Shubra and El-Tebin. GR and GPx activities increased in livers and kidneys of C. lazera collected from all areas except for Shubra, in which, GPx of livers and kidneys were low in 100% of C. lazera. Metals Ni, Co, Cr, Se, Cd and Pb resulting from industrial wastes and metal mining wastes were enhanced at the polluted sites. SDS-PAGE of liver and kidney of O. niloticus and C. lazera indicated the increase in bands number and intensity of protein bands with subunit molecular weights between 30–20 KDa in polluted areas. Several enzymes from glutathione system (activity and protein) constitute a sensitive biochemical indicator of chemical pollution. Relative changes of glutathione-dependent enzymes in both fish species suggest a different susceptibility to toxins.