BACKGROUND: Excessive deposition of extracellular matrix (ECM) in the kidney is the hallmark of diabetic nephropathy. Increased matrix synthesis has been well documented but the effects of diabetes on degradative pathways, particularly in the in vivo setting. The renal protective effect of these pathways on matrix accumulation has not been fully elucidated. The present study was undertaken to investigate the activity of matrix metalloproteinase-2 (MMP-2), the expression of MMP-2 and tissue inhibitor of metalloproteinase-2 (TIMP-2) in kidney tissues of diabetic rats, and to explore the degradative pathway of type IV collagen (IV-C) and the renal protective effects of ACE inhibition-benazepril. METHODS: Twenty-four healthy male Wistar rats were divided randomly into normal control group (NC group), untreated diabetes mellitus group (DM group), and diabetes mellitus group treated with benazepril (DL group). The rat model of diabetes mellitus was induced by intraperitoneal injection of streptozocin (60 mg/kg). After the establishment of DM model, benazepril (10 mg.kg(-1).d(-1)) was given to the DL group for 12 weeks, and the same volume of water was given to the other two groups. At the end of 12 weeks, renal function was evaluated with 24-hour urinary protein (Upro), clearance of creatinine (Ccr), and blood urea nitrogen (BUN). MMP-2 activity was determined by gelatin zymography. The levels of MMP-2, TIMP-2 and collagen IV (IV-C) protein in the kidney tissue were assessed by immunohistochemistry. The gene expression of MMP-2 and TIMP-2 was measured by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: The levels of BUN, Upro and Ccr in the DM group were higher than those in the NC group. In the DM group, the mRNA, enzymatic activity and proteins of MMP-2 decreased, but the expressions of IV-C and TIMP-2 increased. All diabetes-associated changes in renal function and MMP/TIMP were attenuated after benazepril treatment with reduced IV-C accumulation. CONCLUSIONS: The changes of MMP-2 and TIMP-2 expressions in kidney tissues of diabetes rats may contribute to the occurrence and progression of diabetic nephropathy. Benazepril could exert protective effects on diabetic nephropathy, owing to the upregulation of MMP-2 and downregulation of TIMP-2 expressions, which further inhibits the excessive deposition of extracellular matrix in the glomerulus.