Dose-dependent effect of captopril on aortic reactivity of streptozotocin-diabetic rats.

Diabetes mellitus is a primary risk factor for cardiovascular disorders. Strategies that interrupt the renin-angiotensin system have been known to reduce cardiovascular disease. The present study was performed to investigate the effect of sub-chronic administration of captopril on the aortic reactivity of streptozotocin-diabetic rats. Streptozotocin-diabetic rats received captopril (30 and 50 mg/kg per day) for 2 months. Contractile responses to phenylephrine (PE) and relaxation responses to acetylcholine (ACh) and isosorbide dinitrate (ISD) were obtained from aortic rings. Concentration-response curves from captopril-treated diabetic rats to PE were attenuated compared with vehicle (Saline)-treated diabetic rats, especially at a dose of 50 mg/kg captopril. In addition, endothelium-dependent relaxation responses induced by ACh were significantly higher in captopril-treated diabetic rats compared with diabetic rats. The endothelium-independent relaxation responses for ISD were found not to be significantly different among the groups. Therefore, sub-chronic treatment of diabetic rats with captopril in a dose-dependent manner could prevent the functional changes in vascular reactivity in diabetic rats.