The Role of Oxidative Stress in Modulation of the Relaxant Responses of Saphenous Vein and Internal Mammary Artery

Altered endothelial activity is enumerated amongst the leading causes of graft dysfunction following coronary artery bypass surgery and may account for differences in patency between arterial and venous grafts. This study investigates whether differences exist between basal endothelial functions of saphenous vein (SV) and internal mammary arteries (IMA) and explores the putative involvements of reactive oxygen species in this phenomenon. Basal relaxations were greater in IMA than SV. Specific inhibitor of nitric oxide synthase (L-NAME) attenuated dilatory responses while a superoxide anion scavenger (Tiron) displayed a positive effect in both vessel types. MnTBAP, a superoxide dismutase mimetic, improved relaxation in the SV only whereas specific inhibitors of pro-oxidant enzyme NADPH oxidase and cGMP pathway reduced that of the IMA. Rotenone, allopurinol and indomethacin diminished relaxations in the IMA but accentuated SV dilatation. In conclusion, the greater intrinsic antioxidant capacity may explain why IMA make better conduits than SV.