Papel de los radicales libres en el ejercicio físico agotador. Efecto de la administración de antioxidantes.

Laburpena

The beneficial effects of regular, nonexhaustive physical exercise have been known for a long time. Exercise is part of the treatment of common diseases such as diabetes mellitus or coronary heart disease. It improves plasma lipid profile, increases bone density, and helps to lose weight. However, the beneficial effects of exercise are lost with exhaustion and with lack of training. Indeed, it is well known that exhaustive exercise causes muscle damage, for instance evidenced as an increase in the plasma activity of cytosolic enzymes such as creatin kinase or lactate dehydrogenase. Some of this damage is due to the production of reactive oxygen species (ROS) and it may be prevented by optimising nutrition, particularly by increasing the dietary content of nutritional antioxidants. However recent evidences support the idea that ROS play a role in cell signalling and in the adaptations of skeletal muscle to physical exercise. In this thesis we estudied the role of free radicals, derived from the xanthine oxidase, in the activación of the MAPKinases pathway, in the signalling cascade that leads to the activation of NF-?B and in the expression of the genes involved in adaptations to physical exercise (MnSOD, iNOS and eNOS). The results obtained confirm that ROS produced during physical exercise act as signals that are important in muscle cell adaptation to exercise in animals and in humans. Preventing oxidative stress associated with exercise by oral antioxidant administration could be detrimental by hampering the adaptive response. The usual practice of recommending antioxidant supplements before exercise should be seriously questioned. Oral antioxidant supplementation is probably useful before competition when exercise is likely to be exhaustive and damaging, but it may not be so suitable when training.