Alterações eritrocitárias induzidas pelo exercício físico

Abstract

Growing evidence has shown that exercise impairs erythrocyte membrane structure as a consequence of increased physical and chemical stress. Erythrocyte-derived nitric oxide (NO) affects membrane fluidity, and its bioavailiability depends on the balance between its synthesis and scavenging by reactive oxygen species. Here, we investigated whether aerobic exercise performed at different intensities would affect erythrocyte NO bioavailability and oxidative stress. Ten men (26 ± 4 years old, VO2peak 44.1 ± 4.3 mL.kg-1.min-1) performed a treadmill maximal cardiopulmonary exercise test, and a submaximal exercise at 70% VO2peak during 30 min. Blood was collected at rest and immediately after exercises for erythrocytes isolation. Maximal exercise increased erythrocytes count, haemoglobin and haematocrit levels, without any change in body mass that could suggest haemoconcentration due to a plasma volume reduction. It was observed a decrease in L-arginine influx after moderate, but not maximal exercise. Yet, nitric oxide synthase activity, and thus, NO production, was increased after maximal exercise. Cyclic GMP levels did not change after both exercise bouts. In relation to biomarkers of oxidative stress, moderate exercise reduced protein oxidation, and increased catalase activity and glutathione peroxidise expression; whereas maximal exercise led to greater lipid peroxidation, and diminished SOD activity. Neither glutathione peroxidase activity nor NADPH expression were affected by exercise. These findings suggest that exercise induced changes in erythrocyte oxidative stress are more associated with intensity than duration. Furthermore, at intensities recommended for health promotion, exercise was shown to be protective, increasing the activity and expression of important antioxidant enzymes and reducing oxidative damage.