Plasma interleukin-6 during strenuous exercise: role of epinephrine

Exercise induces increased levels of plasma interleukin-6 (IL-6) as well as changes in the concentration of lymphocytes and neutrophils. The aim of th is study was to investigate a possible role for epinephrine. Seven healthy men participated in an exercise experiment. One month later they received a n epinephrine infusion. The exercise consisted of treadmill running at 75% of maximal O-2 consumption for 2.5 h. The infusion trial consisted of 2.5 h of epinephrine infusion calculated to reach the same plasma epinephrine le vels seen during the exercise experiment. The plasma concentration of IL-6 increased 29-fold during exercise, with peak levels at the end of exercise. The increase in plasma IL-6 during epinephrine infusion was only sixfold, with the peak value at 1 h after infusion. The lymphocyte concentration inc reased to the same levels during exercise and epinephrine infusion. The lym phocyte count decreased more in the postexercise period than after epinephr ine infusion. The neutrophil concentration was elevated threefold in respon se to exercise, whereas no change was found in response to epinephrine infu sion. In conclusion, the exercise-induced increase in plasma IL-6 could not be mimicked by epinephrine infusion. However, epinephrine induced a small increase in IL-6 and may, therefore, partly influence the plasma levels of IL-6 during exercise. In addition, the results support the idea that epinep hrine plays a role in exercise-induced changes in lymphocyte number, wherea s epinephrine does not mediate exercise-induced neutrocytosis.