REACTIVE OXYGEN SPECIES-INDUCED IMPAIRMENT OF ENDOTHELIUM-DEPENDENT RELAXATION IN RAT AORTIC RINGS - PROTECTION BY L-ARGININE

The protective effect of L-arginine against reactive oxygen species-in duced impairment of endothelium-dependent vasorelaxation was investiga ted in isolated ring preparations of rat aorta. The aortic rings were subjected to reactive oxygen species generated by the electrolysis of the bathing solution or incubation with H2O2. Endothelium-dependent re laxation in response to acetylcholine of precontracted aortic rings wa s attenuated when the rings were exposed to reactive oxygen species or H2O2. Incubation prior to electrolysis with either L-arginine, the en dogenous precursor of nitric oxide (NO), or sodium nitroprusside, an e xogenous donor of NO, protected the aortic rings against the impairmen t of endothelium-dependent relaxation. However, D-arginine and glycine , amino acids which do not produce NO, also afforded protection in thi s model. Therefore, not only the increased synthesis of NO but also th e oxidation of L-arginine, with concomitant disproportionation of reac tive oxygen species, may be responsible for the protective effect agai nst reactive oxygen species-induced loss of the endothelial response t o acetylcholine in isolated rat aorta.