Heterogeneous vasodilator responses of human limbs: Influence of age and habitual endurance training

Forearm endothelium-dependent vasodilation is impaired with age in sedentary, but not endurance-trained, men. The purpose of this investigation was to determine whether these age- and physical activity-related differences in endothelium-dependent vasodilation also occur in the leg. Brachial and common femoral arterial blood flow were measured with Doppler ultrasound during increasing doses of acetylcholine (1, 4, and 16 1 μg · 100 ml limb tissue^-1 · min^-1), substance P (8, 31, and 125 pg·100 ml limb tissue^-1· min^-1), and sodium nitroprusside (0.063, 0.25, and 1 μg · 100 ml limb tissue^-1 · min^-1) in 23 healthy men (8 younger sedentary, 8 older sedentary, and 7 older endurance trained). Increases in forearm blood flow to the highest dose of acetylcholine and sodium nitroprusside were smaller (P < 0.05) in older sedentary (841 ± 142%, 428 ± 74%) compared with younger sedentary (1,519 ± 256%, 925 ± 163%) subjects. Similarly, increases in forearm blood flow to sodium nitroprusside (1 μg · 100 ml limb tissue^-1 · min^-1) were smaller (P < 0.05) in older endurance-trained (505 ± 110%) compared with younger sedentary (925 ± 163%) subjects. In contrast, no differences in leg blood flow responses to intra-arterial infusions of acetylcholine, substance P, or sodium nitroprusside were noted between subject groups. These results demonstrate that 1) acetylcholine-and sodium nitroprusside-induced vasodilation are attenuated in the forearm vasculature and preserved in the leg vasculature of older sedentary subjects and 2) sodium nitroprusside-induced vasodilation remains attenuated in the forearm vasculature of healthy older endurance-trained men but preserved in the leg vasculature of these men.