['Aging is associated with increased cardiovascular risk and endothelial dysfunction. Since exercise can improve endothelium-dependent vasodilation, in the present study we tested whether long-term physical activity could prevent aging-related endothelial dysfunction.', 'In 12 young and elderly (age 26.9+/-2.3 and 62.9+/-5.8 years, respectively) healthy sedentary subjects and 11 young and 14 elderly matched athletes (age 27.5+/-1.9 and 66.4+/-6.1 years, respectively), we studied (with strain-gauge plethysmography) forearm blood flow modifications induced by intrabrachial acetylcholine (0.15, 0.45, 1.5, 4.5, and 15 microg/100 mL per minute), an endothelium-dependent vasodilator, at baseline, during infusion of N(G)-monomethyl-L-arginine (L-NMMA) (100 microg/100 mL forearm tissue per minute), a nitric oxide-synthase inhibitor, vitamin C (8 mg/100 mL forearm tissue per minute), an antioxidant, and finally under simultaneous infusion of L-NMMA and vitamin C. The response to sodium nitroprusside (1, 2, and 4 microg/100 mL forearm tissue per minute) was also evaluated. In young athletes and sedentary subgroups, vasodilation to acetylcholine was inhibited by L-NMMA and was not changed by vitamin C. In elderly subjects, vasodilation to acetylcholine was blunted as compared with young subjects in both control subjects and athletes, whereas the response to sodium nitroprusside was similar. Moreover, in elderly athletes, vitamin C did not change the vasodilation to acetylcholine. In contrast, in elderly sedentary subjects, the response to acetylcholine was resistant to L-NMMA. In this subgroup, vitamin C increased the vasodilation to acetylcholine and restored the inhibiting effect of L-NMMA.'] Does physical activity prevent age-related impairment in nitric oxide availability in elderly athletes?