Abstract: ［Abstract］ ObjectiveTo observe the changes of serum urea nitrogen(BUN), creatinine(Cr) in paraquat poisoning rats， and to study the mechanism of paraquatinduced renal injury in rats， the expression changes of transforming growth factorβ1（TGFβ1） to assess the protective effect of melatonin in paraquat poisoning. MethodsNinety adult healthy SpragueDawley(SD) rats were divided into three groups randomly, 30 rats in each group. Control group and poisoned group were treated intragastrically with 1mL of paraquat(50 mg/kg) diluted with normal saline. Control group were treated with the same dose of normal saline as poisoned group and melatonin group. melatonin group were given 1 mL of melatonin at a dose of 10 mg/kg diluted with normal saline(once daily, intraperitoneally). Control and poisoned group were treated with the same dose of normal saline(once daily, intraperitoneally) as melatonin group. Six rats in each group were sacrificed on the 1st, 3rd, 5th, 7th and 14th day after exposure. Blood samples were taken from the heart to observe the changes of plasma BUN and Cr. The expression of TGFβ1 in rat renal tissue was detected by immunohistochemistry. ResultsThe BUN of the rats in the poisoned group was significantly higher than that in the control group at each time point， melatonin group BUN at all time points were lower than the poisoned group，but still higher than the control group. BUN in the poisoned group and melatonin group continued to increase from day 1 to day 5, and gradually decreased on the 7th day, the difference was statistically significant（P＜005）. The Cr concentration in the poisoned group was higher than that in the control group at each time point. Except for the first, 3 days to 14 days in  days group were lower than that in poisoned group(P＜005), but still higher than that in control group, and there was no significant difference between control group at each time point(P＞005). The Cr in the poisoned group and the melatonin group continued to increase from day 1 to day 5, and gradually decreased on the 7th day, the difference was statistically significant（P＜005）. The levels of TGFβ1 in the poisoned group were higher than those in the control group at each time point，melatonin group was lower than that of the control group except the 3rd day, but still higher than the control group, the difference was statistically significant（P＜005）. ConclusionTGFβ1 is involved in the pathogenesis of paraquat poisoning kidney injury. melatonin has protective effect on paraquat poisoning kidney tissue, which might be mediated by TGFβ1 in the paraquat induced renal injury，but its regulation path still need a further exploration．

Key words: paraquat, poisoning, melatonin