The current study was conducted in two different locations, the first S1 before the Kut barrier and the second S2 after the Kut barrier at the Tigris River. The study focused on knowing the effect of heavy metals (Pb and Cd)on gene expression of antioxidant genes in Common carp Cyprinuscarpiofor the period from January to September 2021.In the current study, high concentrations of lead and cadmium were recorded in the meat of common carp fish caught from the second site compared to the first site, where the highest value of Lead and Cadmium was recorded in the second site amounted to 9.8, 12.8 µg/gm respectively, While the lowest value was recorded in the first site, it reached 0.05, 0.3 µg/gm respectively. The percentage of gene expression for the antioxidant enzymes SOD and GPX was studied in the blood of common carp, where the lowest gene expression was 1.3 and 1.4 for the fish caught from the first site of the enzyme SOD and GPX respectively, while the highest gene expression was 2.6 and 6.6 at the second site of the enzyme SOD and GPX respectively.It was concluded from the present results that the gene expression of antioxidant enzymes(SOD,GPX ) can be relied upon as indicators of water pollution with heavy metals.

Common carp, lead, cadmium, antioxidant genes, Tigris River, SOD, GPX.