Effects of Dietary Cadmium on the Respiratory Burst of Phagocytes and the Antioxidant Defense in Cultured Red Seabream (Pagrus major)

To examine effects of cadmium on the respiratory burst of kidney phagocytes and antioxidant defense in liver, juvenile red seabream Pagrus major were fed a cadmium-incorporated diet $(1g\;CdC1_2/kg\;diet)$. The respiratory burst activity measured by chemiluminescence (CL) was significantly reduced by oral intake of cadmium. Lipid peroxidation in liver expressed as thiobarbituric acid reactive substances (TBARS) was significantly higher in the fish fed a cadmium-incorporated diet than that of the fish fed a control diet both on Day 3 and Day 9. Liver Glutathione S-transferase (GST) activitiy was significantly increased both on Day 3 and Day 9 by feeding a cadmium-incorporated diet, when compared with the controls. From the present results, it can be concluded that oral intake of cadmium in red seabream is associated with marked reduction of respiratory burst capacity of kidney phagocytes which can elevate susceptibility of fish against infecting pathogens. Cadmium administration also elicits significant increment of lipid peroxidation in liver, and fish try to detoxify cadmium by increasing GST activity.