Changes in plasma nitric oxide metabolites concentration during glucose tolerance test in type 2 diabetic rats

Introduction: Repeated hyperglycemia play an important role in the development of atherosclerosis in diabetic patients. Endothelium is the organ of the first-line defense against atherosclerosis and nitric oxide has a major role in this task. The aim of this study was to determine changes in plasma nitric oxide metabolites concentration during glucose tolerance test in type 2 diabetic rats. Methods: Male neonate Wistar rats divided into control and diabetic groups. Type 2 diabetes was induced by administration of Streptozotocin (100 mg/kg) to neonate rats at day 2. Plasma glucose and nitric oxide concentration were measured at 7, 30, 45, 60, and 75 days. Intravenous glucose tolerance test was done in adults rats and blood samples were collected in 0 and 5, 10, 30, and 60 min after glucose infusion for determining plasma glucose, insulin, and nitric oxide metabolites. Two-way mixed (between-within) ANOVA was used for comparing data. Results: In control group plasma glucose was returned to basal values 60 min after glucose injection while in diabetic rats it was higher than basal levels (P<0.001). After glucose injection, plasma insulin concentration was increased to 4.5 and 1.9 folds in control and diabetic groups respectively. Basal nitric oxide metabolites concentration was higher in diabetic rats (50.4 ± 6.4 vs. 28.8 ± 3.8 mol/l, P<0.05). During glucose tolerance test there was 35 and 62 % fall in plasma nitric oxide concentration in control and diabetic groups respectively. This reduction return to basal values after 30 min in control group while, in diabetic rats it was 17% less than basal levels in 60 min after glucose injection. Conclusions: Decreased nitric oxide production or increased its degradation may be underlying endothelium dysfunction and atherosclerosis in type 2 diabetes.