The effects of chronic L-arginine treatment on vascular responsiveness of streptozotocin-diabetic rats

In this study, the protective effects of L-arginine treatment in vivo on va scular reactivity of streptozotocin (STZ)-induced 12-week-old diabetic rats were examined. Loss of weight, polydipsia, polyphagia, hyperglycemia, hypo insulinemia, and elevated levels of plasma cholesterol and triglyceride wer e observed in diabetic rats. L-arginine treatment (1 mg/mL in drinking wate r) did not significantly affect these metabolic and biochemical abnormaliti es. Plasma malondialdehyde (MDA) levels in untreated diabetic rats were als o significantly higher than untreated controls. However, L-arginine treatme nt prevented the increase in MDA level of plasma of diabetic rats. Contract ile responses, but not sensitivity to noradrenaline (NA), were significantl y increased in diabetic rats compared to controls. Treatment of diabetic ra ts with L-arginine completely prevented the increase in NA responses. Relax ation response to acetylcholine (ACh), but not to sodium nitroprusside (SNP ), in diabetic aorta has been found to be significantly decreased as compar ed with controls. However, there were no significant differences in pD(2) v alues of acetylcholine in either of the groups. L-arginine treatment increa sed the ACh responses to the control level. All effects of L-arginine on va scular reactivity were found to be specific for diabetic rats and not contr ols. These results suggest that functional abnormalities occurred in aorta from diabetic rat might at least in part result from L-arginine deficiency, and the lipid peroxidation-lowering effect of L-arginine may account for i ts protective effect on vascular reactivity of diabetic rats. (C) 1999 Else vier Science Inc. All rights reserved.