L-Arginine supplementation improves antioxidant defenses through L-arginine/nitric oxide pathways in exercised rats

L-Arginine (L-Arg) supplementation has been shown to enhance physical exercise capacity and delay onset of fatigue. This work investigated the potential beneficial mechanism(s) of L-Arg supplementation by examining its effect on the cellular oxidative and nitrosative stress pathways in the exercised rats. Forty-eight rats were randomly divided into six groups: sedentary control; sedentary control with L-Arg treatment; endurance training (daily swimming training for 8 wk) control; endurance training with L-Arg treatment; an exhaustive exercise (one time swimming to fatigue) control; and an exhaustive exercise with L-Arg treatment. L-Arg (500 mg/kg body wt) or saline was given to rats by intragastric administration 1 h before the endurance training and the exhaustive swimming test. Expression levels and activities of the L-Arg/nitric oxide (NO) pathway components and parameters of the oxidative stress and antioxidant defense capacity were investigated in L-Arg-treated and control rats. The result show that the L-Arg supplementation completely reversed the exercise-induced activation of NO synthase and superoxide dismutase, increased L-Arg transport capacity, and increased NO and anti-superoxide anion levels. These data demonstrate that L-Arg supplementation effectively reduces the exercise-induced imbalance between oxidative stress and antioxidant defense capacity, and this modulation is likely mediated through the L-Arg/NO pathways. The findings of this study improved our understanding of how L-Arg supplementation prevents elevations of reactive oxygen species and favorably enhances the antioxidant defense capacity during physical exercise.