Circulating leucocyte subpopulations in sedentary subjects following graded maximal exercise with hypoxia

Ten healthy sedentary subjects [age, 27.5 (SD 3.5) years; height, 180 (SD 5) cm; mass, 69.3 (SD 6.3) kg] performed two periods of maximal incremental graded cycle ergometer exercise in a supine position. Randomly ordered and using an open spirometric system, one exercise was carried out during normoxia [maximal oxygen consumption ( {Mathematical expression}O_2max)=38.6 (SD 3.5) ml·min^-1·kg^-1; maximal blood lactate concentration, 9.86 (SD 1.85) mmol·l^-1; test duration, 22.6 (SD 2.7) min], the other during hypoxia [ {Mathematical expression}O_2max=33.2 (SD 3.2) ml·min^-1· kg^-1; maximal blood lactate concentration, 10.38 (SD 2.02) mmol·l^-1; test duration, 19.7 (SD 2.8) min]. At rest, immediately (0 p) and 60 min (60 p) after exercise, counts of leucocyte subpopulations (flow cytometry), cortisol and catecholamine concentrations were determined. At 0 p in contrast to normoxia, during hypoxia there was no significant increase of granulocytes. There were no significant differences between normoxia and hypoxia in the increases from rest to 0 p in counts of monocytes, total lymphocytes and lymphocyte subpopulations [clusters of differentiation (CD), CD3⁺, CD4⁺CD45RO^-, CD4⁺CD45RO⁺, CD8⁺CD45RO^-, CD8⁺CD45RO⁺, CD3⁺HLA-DR⁺, CD3^-CD16/CD56⁺, CD3⁺CD16/CD56⁺, CD 19⁺] as well as adrenaline, noradrenaline and cortisol concentrations. The counts of CD3 ^-CD16/CD56⁺-and CD8 ⁺CD45RO⁺-cells increased most. At 60 p, CD3^-CD16/CD56⁺ and CD3⁺CD16/CD56⁺-cell counts were below pre-exercise levels and under hypoxia slightly but significantly lower than under normoxia. We concluded that the exercise-induced mobilization and redistribution of most leucocyte and lymphocyte subpopulations were unimpaired under acute hypoxia at sea level. Reduced increases of granulocyte counts during the study and reduced cell numbers of natural killer cells and cytotoxic, not major histocompatibility complex-restricted T-cells, only indicated marginal effects on the immune system.