Are the relationships between early activation of lymphocytes and cortisol or testosterone influenced by intensified cycling training in men?

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Abstract
The effects of exercise training on lymphocyte responses, as well as changes in circulating endocrine parameters at rest, were investigated. Seven male cyclists participated in a 4 week high-intensity (HI) cycling training intervention. Training improved performance significantly (peak power output (PPO): 1.4%, p < 0.05; 5 km time trial: 3.8%, p < 0.01; 40 km time trial: 0.4%, p < 0.05). Resting hormone concentrations (testosterone, sex hormone binding globulin (SHBG), cortisol, corticosteroid-binding globulin (CBG), and dehydroepiandrosterone-sulphate (DHEA-S)) were unchanged, with the exception of a 20% decrease in testosterone post-HI training (p < 0.067). Subjects' CD3+cell counts decreased by 15% (p < 0.05), owing to significantly decreased CD4+cell counts and slightly lower CD8+and natural killer (NK) cell counts. Spontaneous in vitro CD69 expression increased in CD4+cells (mean ± SD, pre: 12 ± 6 cells·µL-1; post: 35 ± 37 cells·µL-1; p < 0.05), but not in CD8+cells (pre: 20 ± 29 cells·µL-1; post: 33 ± 16 cells·µL-1). Mitogen-induced CD69 expression decreased in both CD4+(pre: 1570 ± 1258 cells·µL-1; post: 596 ± 597 cells·µL-1; p < 0.05) and CD8+lymphocytes (pre: 676 ± 434 cells·µL-1; post: 412 ± 235 cells·µL-1; p < 0.05). Testosterone correlated positively with several immune parameters at baseline, whereas cortisol correlated negatively with parameters of the innate immune system post-HI training. We conclude that the stress of unaccustomed exercise is evident in resting lymphocytes, but not in resting endocrine parameters. However, correlations between testosterone and cortisol and immune parameters suggest that these 2 hormones play a role in modulating immune status. Our results indicate the importance of assessing both spontaneous and mitogen-induced aspects of immune-cell activation.Key words: CD69, DHEA, lymphocytes, exercise.