Effect Of Cadmium On Antioxidant Enzymes And Lipid Peroxidation Of Silurus Meridionalis

To explore toxic action of the cadmium chloride (Cd2+) to antioxidase and lipid peroxidation of southern catfish (Silurus meridionalis Chen), we exposed Juvenile southern catfish to Cd2+(50μg/L,500μg/L,5000μg/L)for 1d,7d,14d,21d,28d. And then, the content of malondialdehyde (MDA) and activities of catalase (CAT), superoxide dismutase(SOD), glutathione peroxidase(GPX) from liver, kidney, gill, brain, heart, intestine and muscle of the treated S. meridionalis were measured. The liver results showed:In 1d and 7d treatment, with the increasing of cadmium concentration, the GPX and CAT activity increased at first and then decreased; while 14d,21d and 28d treatment, the activity of CAT and GPX reduced with the concentrations of cadmium increasing; the activity of CAT and GPX reached to the peak of 500μg/L after Id treatment, the minimum reached to 5000μg/L after 28d treatment. After 1d treatment, SOD activity decreased at first to the peak of 500μg/L, then increased and finally decreased with the increasing of cadmium concentration; however after 7d treatment, it increased firstly and then decreased; to 14d,21d,28d, the liver SOD activity increased to the minimum of 5000μg/L with the decrease of cadmium concentration; while, the MDA content increased with the increasing of cadmium concentration from beginning to end.The catalase (CAT), superoxide dismutase (SOD), glutathione peroxide physical activity (GPX) activity assay from the liver, kidney, brain, heart, muscle, intestine and gills were carried out after 28d treatment of 50μg/L cadmium. The results showed:the CAT activity from liver, kidney, gill, foregut, brain and heart were significantly decreased, while it did not change from muscle; SOD activity from kidney, gill were decreased, from foregut and muscle were increased, while from liver, brain and heart were no change; GPX activity from liver, kidney, gill, foregut, muscle and brain were decreased but no change from heart.In sum, the influence of cadmium to southern catfish liver on antioxidant enzyme system shows as follows:the early stage (1d-7d), antioxidant enzyme activity increased first and then decreased with the increase of cadmium concentration; the late stage (14d-28d), it decreased with the increase of cadmium concentration.The reason can be analyzed as following:in the early stage treatment, southern catfish liver has adaptive response to cadmium toxicity, manifesting the induction of antioxidant enzyme activity; but in the later stage, with the increase of cadmium concentration and exposure time, cadmium toxicity is beyond the liver bear ability of southern catfish, so the antioxidant enzyme activities are decreased. Lipid peroxidation showed an increase with the cadmium concentration increased. Tissue-specific result of antioxidant enzyme activity shows that enzyme activity is closely related to the physiological functions of the tissues.