Background: Skeletal muscle has several physiological functions. One of the most important function is the ability to regulate the redox status through reactive oxygen species (ROS)
production and the modulation of its antioxidant system. Intense exercise practice is the main characteristic of several sports, and is known to be responsible to induce oxidative stress. Nutritional
supplements are commonly used among athletes to increase their performance, and also to reduce some damages that can be caused by intense exercise. L-arginine is a conditionally essential amino acid
that actively contributes to several process, such as: urea synthesis, cellular growth and nitric oxide production. Furthermore, new evidences are proposing that L-arginine could also be beneficial to
skeletal muscle, by regulating some antioxidant enzymes and controlling ROS production. Therefore, the aim of this study was to evaluate the effects of L-arginine supplementation on trained and
untrained rats’ performance and skeletal muscle oxidative stress and antioxidant system.
Methods: It was used 40 male Wistar rats which were divided into 4 groups: control (C), control + L-arginine (CA), trained (T) and trained + L-arginine (TA). After 8 weeks of
endurance training, rats were submitted to an intense exercise section and then immediately euthanized. Maximal velocity and total time of section were used as performance indicators. Oxidative stress
and the antioxidant system were evaluated by the following methods: TBARS, GSH/GSSG ratio, uric acid concentration, iron, nitrate and activities of antioxidant enzymes (superoxide dismutase, catalase
and glutathione peroxidase).
Results: It was found that L-arginine supplementation has improved rats’ performance, mainly when associated to training. Additionally, L-arginine and exercise training reduced some
oxidative stress biomarkers. This response was exacerbated when they were associated. Supplementation and exercise training were alone capable to increase glutathione peroxidase activity. When
combined, besides glutathione peroxidase, catalase activity was increased as well.
Conclusions: We concluded that L-arginine could be a good strategy to sports practitioners, being able to improve their performance and attenuating some damages that can be caused by
oxidative stress. Studies in humans are now need to be carried out to confirm this hypothesis.