Plasma interleukin-6 during strenuous exercise: role of epinephrine

Exercise induces increased levels of plasmainterleukin-6 (IL-6) as well as changes in the concentration oflymphocytes and neutrophils. The aim of this study was to investigate apossible role for epinephrine. Seven healthy men participated in anexercise experiment. One month later they received an epinephrineinfusion. The exercise consisted of treadmill running at 75% ofmaximal O₂ consumption for 2.5 h. The infusion trialconsisted of 2.5 h of epinephrine infusion calculated to reach thesame plasma epinephrine levels seen during the exercise experiment. Theplasma concentration of IL-6 increased 29-fold during exercise, with peak levels at the end of exercise. The increase in plasma IL-6 duringepinephrine infusion was only sixfold, with the peak value at 1 hafter infusion. The lymphocyte concentration increased to the samelevels during exercise and epinephrine infusion. The lymphocyte countdecreased more in the postexercise period than after epinephrineinfusion. The neutrophil concentration was elevated threefold inresponse to exercise, whereas no change was found in response toepinephrine infusion. In conclusion, the exercise-induced increase inplasma IL-6 could not be mimicked by epinephrine infusion. However,epinephrine induced a small increase in IL-6 and may, therefore, partlyinfluence the plasma levels of IL-6 during exercise. In addition, theresults support the idea that epinephrine plays a role inexercise-induced changes in lymphocyte number, whereas epinephrine doesnot mediate exercise-induced neutrocytosis.