780-2 Exercise Increases Systemic Nitric Oxide Production in Men

Abstract

The effects of submaximal exercise on systemic nitric oxide (NO) formation, as assessed by measuring the urinary excretion rates of NO - 3 and of cyclic GMP, were compared in 10 endurance-trained and 6 untrained male subjects. Urinary excretion rates of NO - 3 (by gas chromatography) and cyclic GMP (by radioimmunoassay) were assesse before and after a 30 min exercise test dlt 60% of each subject's individual maximal work capacity in hourly intervals. Urinary NO - 3 excretion in untrained and trained subjects was comparable at rest (104 ± 35 vs. 110 ± 19 μmol/mmol creatinine, p = n.s.). It more than doubled during exercise in both groups (to 236 ± 88 μmol/mmol creatinine in untrained and to 252 ± 39 μmol/mmol creatinine in trained subjects, each p < 0.01) and rapidly decreased to baseline within 2 hours after the test. Resting urinary cyclic GMP excretion was fourfold higher in the athletes than in the untrained subjects (21 ± 5 vs. 6 ± 1 nmol/mmol creatinine, p < 0.05). During exercise it increased about twofold in both groups (to 52 ± 12 and 10 ± 1 nmol/mmol creatinine, respectively, each p < 0.01), and returned to baseline after its end. There was a correlation between urinary cyclic GMP and NO - 3 excretion (p < 0.05) in both groups. We conclude that acute submaximal exercise increases the formation of NO in man, as reflected by the increased urinary excretion of NO - 3 and cyclic GMP. This may contribute to the vasodilation during physical exercise, and at least partly explain the beneficial effects of physical training in patients with cardiovascular diseases.