Alterations in intracellular calcium signaling of lymphocytes after exhaustive exercise

Purpose: Exhaustive exercise is accompanied by pronounced quantitative chan ges in leukocytes. Whereas most studies on lymphocytes have concentrated on their proliferative responses or cytokine secretion, not much is known abo ut exercise-induced changes in intracellular signal transduction processes. In lymphocytes, the concentration of intracellular free calcium ([Ca2+](i) ) is an important intracellular second messenger linking extracellular stim uli to cellular responses. The aim of the present study was to examine the effect of exhaustive exercise on the calcium homeostasis of lymphocytes. Me thods: Healthy volunteers underwent treadmill exercise at 80% of their maxi mal oxygen uptake until exhaustion. Blood samples were taken before, immedi ately after, 1 h after, and 1 d after the rest. Lymphocyte subsets were ana lyzed by flow cytometry; isolation of lymphocytes was performed by density gradient centrifugation. [Ca2+](i) was measured using the calcium-sensitive fluorescent dye Fura-2. Results: Compared with preexercise conditions, bas al [Ca2+](i) was increased immediately after exercise, whereas there was no change after i h or 1 d. The anti-CD3- and phytohemagglutinin-induced Ca2 responses demonstrated a bivalent pattern. Immediately after exercise, Ca2 + transients were impaired, whereas 1 h after and 1 d after the test, the C a2+ responses were increased. In contrast, the Ca2+ responses induced by rh apsigargin were not different at any time interval. Lymphocyte subsets incr eased immediately after exercise, especially natural killer cells and CD8T cells, and decreased below preexercise levels after 1 h. One day after ex ercise, cell counts were not different from preexercise levels. Conclusions : Taken together, this novel approach demonstrates that exhaustive exercise has a profound influence on intracellular calcium signaling of lymphocytes . These effects may explain changes in lymphocyte function that have previo usly been reported.