BOTH PHYSICAL-FITNESS AND ACUTE EXERCISE REGULATE NITRIC-OXIDE FORMATION IN HEALTHY HUMANS

We analyzed nitrate, a major stable end product of nitric oxide (NO) m etabolism in vivo in plasma and urine from groups of healthy subjects with different working capacities. Resting plasma nitrate was higher i n athletic subjects than in nonathletic controls [45 +/- 2 vs. 34 +/- 2 (SE) mu M; P < 0.01]. In other subjects, both the resting plasma nit rate level (r = 0.53; P < 0.01) and the urinary excretion of nitrate a t rest (r = 0.46; P < 0.01) correlated to the subjects' peak work rate s, as determined by bicycle ergometry. Two hours of physical exercise elevated plasma nitrate by 18 +/- 4 (P < 0.01) and 16 +/- 6% (P < 0.01 ), respectively, in athletes and nonathletes, compared with resting ni trate before exercise. We conclude that physical fitness and formation of NO at rest are positively linked to each other. Furthermore, a sin gle session of exercise elicits an acute elevation of NO formation. Th e observed positive relation between physical exercise and NO formatio n may help to explain the beneficial effects of physical exercise on c ardiovascular health.