Résumé
AIM To determine the relationship between the elevation of endogenous inhibitor of nitric oxide synthase (NOS)N G,N G-asymmetric dimethylarginine (ADMA) and metabolic control in diabetic rats. METHODS Diabetes was induced in Sprague-Dawley rats by a single intraperitoneal injection of streptozotocin. At 72 h after injection, half of diabetic rats received insulin treatment for 8 weeks (20 U?kg -1?d -1,ih, bid). Serum levels of ADMA were measured by high-performance liquid chromatography. Thoracic aortic rings from non-diabetic age-matched control, untreated diabetic, and insulin-treated diabetic rats were tethered in isolated organ baths,contracted with 1 ?mol?L -1 phenylephrine, and challenged with either the endothelium-dependent vasodilator acetylcholine or the endothelium-independent vasodilator sodium nitroprusside. Serum concentrations of glucose, glycosylated serum protein, and malondialdehyde, derived from lipid peroxidation were also examined to estimate metabolic control.RESULTS Serum levels of ADMA significantly elevated in untreated diabetic rats compared with control rats. This elevation of ADMA was accompanied by impairment of relaxation response to acetylcholine but not sodium nitroprusside in aortic rings. Chronic insulin treatment not only prevented the elevation of serum ADMA, but also improved the impaired endothelium-dependent relaxation in diabetic rats. Serum levels of glucose, glycosylated serum protein, and malondialdehyde were significantly increased in parallel with the elevation of ADMA in untreated diabetic rats compared with control rats. These parameters were normalized after diabetic rats received insulin treatment. CONCLUSION These results provide the first evidence that the elevation of endogenous inhibitor of NOS in streptozotocin-induced diabetic rats is close related to metabolic control of the disease.