Abstract: ObjectiveTo study the effect of different dosage KIon the anti-oxidative capability of blood.MethodThe rats were divided into 6 groups and given by different dosage of KI,which were low iodide(LI),normal iodide(NI),5 fold high iodide(5HI),10 fold high iodide(10HI),50 fold high iodide(50HI)and 100 fold high iodide(100HI).Three,6 and 12 months later,the rats were sacrificed and blood glutathione peroxidase(GPx)activity,superoxide dismutase(SOD) activity and malondialdehyde(MDA)content were measured.ResultsAfter treatment for 3 and 6 months,the GPx activity in LI group was markedly lower than thatin NI group.Furthermore,after 6 months for low iodine intake,the MDA content in LI group was higher than thatin NI group.The GPx activity in 100HI group was lower than thatin NI group after administration for 3 months,but no difference between these two groups after treatment for 6 and 12 months,no difference was found in the GPx activity of NI group and those of 5HI,10HI and 50HI groups.There was no difference in SOD activity and MDA content among NI group and 4 high iodide groups.ConclusionLow iodide intake would damage the anti-oxidative capability of blood in normal rats.Blood had a strong anti-oxidative ability and compensative capabilities to compete with high iodide intake.