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1 Department of Integrative Physiology, University of Colorado-Boulder, Boulder, Colorado, United States
2 Division of Cardiology H047, Penn State College of Medicine, Hershey, Pennsylvania, United States
* To whom correspondence should be addressed. E-mail: tony.donato{at}colorado.edu.
Resting whole-leg blood flow and vascular conductance decrease linearly with advancing age in healthy adult males. The potential role of oxidative stress in these changes is unknown. Ten young (25±1 years) and 11 older (63±2 years) healthy normotensive men were studied. Plasma oxidized LDL, a marker of oxidative stress, was greater in the older men (P<0.05). Absolute resting femoral artery blood flow at baseline (i.v. saline control infusion) was 25% lower in the older men (238±25 vs. 316±38 ml·min-1, P<0.05), and inversely related to plasma oxidized LDL (r=-0.56, P<0.01) in all subjects. Infusion of supra-physiological concentrations of ascorbic acid increased femoral artery blood flow by 37% (to 327±52 ml·min-1) and vascular conductance by 36% in the older men (P<0.05), but not in the young men, thus, abolishing group differences. Mean arterial blood pressure was greater in the older men at baseline (86±4 vs. 78±2 mmHg, P<0.05), but was unaffected by ascorbic acid infusion (P
0.70). As a result, the lower baseline femoral artery blood flow in the older men was mediated solely by a 32% lower femoral artery vascular conductance (P<0.05). Baseline femoral vascular conductance also was inversely related to plasma oxidized LDL (r=-0.65, p<0.01). In conclusion, ascorbic acid infused at concentrations known to scavenge reactive oxygen species restores resting femoral artery blood flow in healthy older adult males by increasing vascular conductance. These results support the hypothesis that oxidative stress plays a major role in the reduced resting whole-leg blood flow and increased leg vasoconstriction observed with aging in men..
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