Abstract： Objective To sutdy the protective mechenism of Captopril on the kidney of diabetic rats.Methods Male Sprague-Dawley rats,rendered to be diabetic with streptozocin (STZ),were treated with captopril dissolved in dringing water for 12 weeks.The serum creatinine,blood urea nitrigen (BUN),proteinuria,blood malondialdehyde(MDA),and the content of NO,cAMP,and advanced glycosylation end products (AGEs) in renal tissue were measured.The renal pathological lesions and the expression of TGFβ 1 were also investigated.Results Captopril supplementation reduced the serum creatinine and proteinuria.The abnormal changes in kidney morphology were ameliorated.The blood MDA,the expression of TGFβ 1 and the content of AGEs in the test group were significantly lower than controlled diabetic rats,the renal NO and cAMP were enhanced.Conclusion Administration of Captopril to rats with STZ-diabeties could ameliorate diabetic nephropathy.This beneficial effect could be related to reduced oxidant injury,less accumulation of AGEs,inhibition of the expression of TGFβ 1,and enhance renal NO and cAMP.