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The participation of superoxide in initiating tissue damage from administration of a xenobiotics is best illustrated by paraquat intoxication. Paraquat, a widely used herbicide, is extremely toxic, causing multiple organ failure in human and may result in death. In the present study, the toxicity of paraquat on pregnant mice was investigated. The mortality of paraquat treated-pregnant mice was significantly increased compared with that of non-pregnant female mice and in pregnant mice, the mortality of fetus was more severe than mother. Natural defence mechanisms against oxygen free radical damage include superoxide dismutase (SOD), which eliminates superoxide radicals; catalase and glutathion peroxidase, which eliminates hydrogen peroxide. In this experiment, we measured the activities of SOD, catalase and glutathione peroxidase in liver, uterus, placenta and fetus in paraquat administrated mice. In liver, the activities of SOD and glutathione peroxidase were significantly decreased by paraquat administration but catalase was not significant in non-pregnant, whereas in pregnant mice, all enzymes are significantly decreased by administration of paraquat. In pregnant mice, the level of antioxidant enzymes in uterus, fetus and placenta were lower than in liver but the levels of glutathione peroxidase was significantly elevated in placenta. The antioxidant enzymes in uterus, fetus and placenta were decreased more significantly than in liver by paraquat. These results suggest that the increased paraquat toxicity in pregnant mice and fetus compared with mother is probably due to a decrease of the activities of antioxidant enzymes especially catalase.
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