Phagocytes may counteract the "open window" situation during a bout of moderate exercise performed by sedentary individuals: role of noradrenaline

Changes in the blood number of peripheral lymphocytes, monocytes and granulocytes at different times (basal, at 7 min, and immediately after exercise) during moderate exercise (55% VO2 max; 60 min) performed by sedentary men were investigated. These variations were also evaluated during a recovery period (45 min and 24 h after finishing the exercise), and were correlated with changes in catecholamines and cortisol. The T (total CD3+, CD4+, and CD8+) and B (CD19+) lymphocytes showed similar behaviour during exercise, although the changes were more marked in T cells: an increase 7 min after the start of exercise that returned to the basal values immediately after exercise, and then a decrease (below basal) 45 min later to return again to the basal values 24 hours after the beginning of the physical activity. However, this behaviour was not shown by monocytes (CD14+) and granulocytes (CD15+), which increased their number from the beginning of the exercise and reached their highest values immediately after finishing it. NK cells (CD16+) showed an intermediate behaviour between lymphocytes and phagocytic cells, with the highest values during exercise and the lowest ones (below basal) 45 min after the end of the physical activity. The profile in the plasma concentration of noradrenaline during the study correlated mainly with the profiles in the number of phagocytic cells, especially of monocytes. No significant correlations were found with adrenaline and cortisol.It is concluded that, as previously reported for intense exercise, a bout of moderate exercise performed by sedentary individuals provokes changes in the incidence of lymphocytes and NK cells according to the "open window" theory. Phagocytic cells may couteract the "open window" situation, with the mechanism involving noradrenaline.