Abstract: For clarifying some possible mechanism of cadmium toxicity, the effect of increasing amounts of Cd2+ ion on peroxidase activity was investigated in vitro in serum of cow. The H2O2-mediated oxidation of o-dianisidine was used to assess the peroxidase activity. Results show that after preincubation of serum with 0.25-100 mM Cd2+ concentration for 5 min, peroxidase activity was inhibited compared to the control and decreased rapidly with increasing metal concentrations. The enzyme was completely inhibited after 5 min preincubation in 100 mM Cd2+. When the preincubation of serum and Cd2+ was prolonged to 0.5, 1 and 24 h, the enzymatic activity decreased more rapidly with increasing metal concentration and the enzyme was completely inhibited at lower metal concentrations (at 50 mM Cd2+ after 30 min preincubation, at 30 mM Cd2+ after 60 min preincubation and at 5 mM Cd2+ after 24 h). By considering of long biological half-life of cadmium in body of animals, it suggested that the damage caused by exposure to heavy metals is often not only dose-dependent, but also time-dependent. Even though detoxifying enzymes may not show any effect after brief exposure to low concentrations of heavy metals, prolonged incubation will affect the enzymatic activity, leading eventually to complete inactivation.
H. Tayefi-Nasrabadi , Gh. Moghaddam , Z. Rajabi and Gh. Dehghan , 2008. Effect of Cadmium Ion on Peroxidase Activity of Serum in Cow: An in vitro Study. Journal of Animal and Veterinary Advances, 7: 866-869.