Oxidative stress explains differences in large elastic artery compliance between sedentary and habitually exercising postmenopausal women

OBJECTIVE: To determine whether oxidative stress contributes to differences in large elastic artery compliance between sedentary and habitually exercising postmenopausal women. DESIGN: Carotid artery compliance was measured during acute intravenous infusions of saline (control) and supraphysiological doses of the potent antioxidant ascorbic acid (vitamin C) in sedentary (n = 15; 58 +/- 1 years) and endurance exercise-trained (n = 11, 59 +/- 1) healthy postmenopausal women. RESULTS: Carotid artery compliance was 24% higher in the exercising versus sedentary women during control (P < 0.001). During ascorbic acid infusion, carotid artery compliance was increased by 28% in the sedentary women (1.29 +/- 0.12 to 1.60 +/- 0.12 mm/mm Hg x 10, P < 0.001 vs control) but was unchanged in exercising women (1.60 +/- 0.14 vs 1.48 +/- 0.14 mm/mm Hg x 10, P = 0.10), abolishing the habitual exercise-associated baseline difference. The change in compliance with ascorbic acid was most strongly related to maximal aerobic capacity (r = -0.64, P < 0.0001) and body fatness (r = 0.60, P < 0.0001) and was more modestly related to oxidized low-density lipoprotein, waist circumference, interleukin-6, total and low-density lipoprotein cholesterol (all r = 0.40 to 0.49, all P < 0.05), and high-density lipoprotein cholesterol (r = -0.48, P = 0.01). Carotid artery diameter, blood pressure, and heart rate were unaffected by ascorbic acid. CONCLUSIONS: These results indicate that the greater large elastic artery compliance in habitually exercising compared with sedentary estrogen-deficient postmenopausal women may be mediated by an absence of oxidative stress, perhaps related in part to more favorable cardiovascular risk factors.