LYMPHOCYTE SUBSET RESPONSES TO EXERCISE AND GLUCOCORTICOID SUPPRESSION IN HEALTHY-MEN

It is well established that in vivo changes in ratios of lymphocyte ph enotype subsets is altered by glucocorticoid administration. To determ ine whether the lymphocyte response would be further affected by stren uous exercise, since glucocorticoids are released during exercise, 14 physically fit men were randomly given placebo (P), 4 mg of dexamethas one (DEX), or 100 mg of hydrocortisone (HCO) 4 h before high-intensity treadmill running. Blood was drawn pre- and immediately post-exercise ; lymphocyte subsets (CD3, CD4, CD8, CD19, and CD56) were determined b y flow cytometry. Pre-exercise CD3 and CD4 percentages were lower, whe reas CD8 and CD56 were higher with DEX and HCO as compared to P. Exerc ise induced a lymphocytosis after all treatments, but subsets did not change proportionally. With P, DEX, and HCO, the magnitudes of change were comparable: CD3 and CD4 decreased and CD8 and CD56 increased. Not ably, for all treatments exercise induced an approximately 2-fold incr ease in the percentage of cells expressing CD56 (natural killer cells) . Thus, a single oral dose of DEX or HCO did not alter the direction o r magnitude of immediate post-exercise changes in lymphocyte subset ex pression. Whether glucocorticoid pretreatment influences lymphocyte re sponses during recovery from strenuous exercise remains to be determin ed.