Positive correlation between plasma nitrite and performance during high-intensive exercise but not oxidative stress in healthy men.

Several studies suggest that exercise is associated with elevated oxidative stress which diminishes NO bioavailability. The aim of the present study was to investigate a potential link between NO synthesis and bioavailability and oxidative stress in the circulation of subjects performing high-intensive endurance exercise. Twenty-two male healthy subjects cycled at 80% of their maximal workload. Cubital venous blood was taken before, during and after exercise, and heparinized plasma was generated. Plasma concentrations of nitrite and nitrate were quantified by GC-MS and of the oxidative stress biomarker 15(S)-8-iso-PGF(2alpha) by GC-MS/MS. pH and pCO(2) fell and HbO(2) increased upon exercise. The duration of the 80% phase (d80) was 740+/-210s. Subjects cycled at 89.2+/-3.3% of their peak oxygen uptake. Plasma concentration of nitrite (P<0.01) and 15(S)-8-iso-PGF(2alpha) (P<0.05) decreased significantly during exercise. At the end of exercise, plasma nitrite concentration correlated positively with d80 and performed work (w80) (each P<0.05). Changes in nitrate concentration also correlated positively with d80 (P<0.05) and w80/kg (P<0.01). These findings provide evidence of a favorable effect of nitrite on high-intensive endurance exercise. The lack of association between 15(S)-8-iso-PGF(2alpha) and NO bioavailability (nitrite concentration) and NO biosynthesis (nitrate concentration) suggest that oxidative stress, notably lipid peroxidation, is not linked to the l-arginine/NO pathway in healthy male subjects being on endurance exercise.