Impairment of plasma nitric oxide availability in senescent healthy individuals: Apparent involvement of extracellular superoxide dismutase activity

Abstract

To verify the potential involvement of the age-dependent modifications of EC-SOD activity in the impairment of plasma NO availability with advancing age, 40 healthy men divided into 4 age groups for the purpose of comparison (young: 27.4±1.5 years; middle: 50.8±2.2, years; old: 70.0±1.8 years; very old: 86.1±1.1 years) were enrolled in this study. Plasma samples were used for measurements of the stable end-product nitrite/nitrate (NO_x), as an expression of NO availability, EC-SOD activity, thiobarbituric acid reactive substances (TBARS) as a marker of lipid peroxidation, low density lipoprotein (LDL) copper-mediated oxidation in vitro and total antioxidant capacity (TEAC). Our results indicated a significant age-related progressive decrease of plasma NO_x content and EC-SOD activity and their values were positively correlated (r=0.713, p<0.001). Increased TBARS amount together with reduced lag time for in vitro oxidation of LDL and decreased content of TEAC were observed with advancing age. Finally, EC-SOD values were negatively correlated with plasma TBARS values (r=−0.855, p<0.001). Findings of the present study suggest that the decrease of antioxidant defence strategies play a primary role by compromising NO availability in normally aged individuals, particularly through a progressive decrease of EC-SOD activity.