Abstract: Objective To investigate the relation of paraquart-induced renal injury and the changes of hemeoxygenase 1(HO-1)exp ression and inducible nitric oxide synthase(iNOS).Methods Eighty-four adult healthy Spragne-Dawley rats were randomly divided into two groups,the control group(n=42)and the paraquart(PQ)poisoning group(n=42).The rats in the paraquart poisoning group were treated with 25 m g/kg PQ in trape ritoneally and the rats in the control group were treated with the same dose of normal saline.Then the histopa thological change,the expression of iNOS,HO-1m RNA were observed.Results Compared with the control group,there were obvious lesions in renal tubule of cortical part,including congestion,edema and vacuolar degene ration in the paraquart poisioning group.These pa thologic changes gradually reached the peak on the 1st day,and did not relieved till the end of the study.Com pared with the control group,the expression of iNOS in the paraquart poisoning group was observed at 3rd hour,reached the pesk on the 1st day with an immunoh is tochemis try score of 8±2.23,and continued at a high level.Com pared with the control group,the expression of HO-1 in the paraquart poisoning group was observed at the 3rd hour with an immunoh isochem is try score(IHS)of 3.33±1.75(P<0.05).The expression of HO-1m RNA increased and reached the peak on the 1st day with a INS score of 7±2(P<0.05).Conclusion H-1 and iNOS were involved in the procees of renal injury induced by paraquart.