Abstract: Objective To study of the tissue distribution of paraquat in rats. Methods Thirty-six male rats were divided into nine groups:the pre-administration group, the 0.5, 1, 3, 6, 10, 24, 48 and 72 hours after administration. The pre-administration group did not give paraquat, and the tissues were directly taken. The post-administration group was given 90 mg/kg paraquat by single administration, and the tissues and plasma were taken at the corresponding time points. Heart, liver, lung, kidney, brain, cerebellum, stomach were taken for homogenate extraction, and paraquat concentration in tissues and plasma was determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results The highest concentration of paraquat in stomach, kidney, lung and liver was more than 30 μg/g, and the highest concentration of paraquat in heart, brain and cerebellum was less than 10 μg/g. The highest concentrations were found in stomach and lung at 1 hour (205.5±69.5) μg/g and (35.5±28.0) μg/g, respectively. The highest concentrations were found in kidney and liver at 3 hours (124.8±146.9) μg/g and (30.9±42.1) μg/g, respectively. Most of the concentration in tissues and plasma varied more than 50% individually, showing higher individual differences. Conclusion The distribution of paraquat in vivo is highly similar with the damage location and degree of target organs after poisoning. The plasma concentration of paraquat can only indirectly reflect of the paraquat in vivo, but can not represent the level of poisons in injured organs. We should pay attention to the damage and failure of target organs in clinical practice, and timely intervention and treatment.

Key words: paraquat, tissue distribution, liquid chromatography-tandem mass spectrometry(LC-MS/MS)