Protection of l-arginine against oxygen free radicals-injured rabbit aortic endothelium

This study was to investigate the protective effect of l-arginine, a precursor of endothelium-derived relaxing factor (EDRF), against damages due to endogenous or exogenous oxygen free radicals (OFR) on the aortic endothelium. The superfusion cascade bioassay of rabbit thoracic aorta was used. Endogenous OFR were generated by diethyldithiocarbamate (DETC) to deplete the cytosolic Zn-Cu form of superoxide dismutase (SOD). Exogenous OFR were generated by electrolysis of Krebs' solution. Acetylcholine (ACh) was infused through the donor aortic segment and relaxation of detector aortic ring was used as an indicator of the release of EDRF. The content of malondialdehyde (MDA) in the donor aorta was assayed biochemically. Both DETC and electrolysis inhibited vasodilator responses to ACh and increased MDA content in the aortic segment. Inhibition of DETC was abolished by exogenous SOD. l-Arginine improved impairment of endothelium-dependent relaxation and reduced elevation of MDA content by DETC or electrolysis. These results suggest that l-arginine presents a protective effect of endothelium against damage due to endogenous or exogenous OFR, and that the protective effect of l-arginine may be correlated with reduction in lipid peroxidation