Regulation of MAC-1 (CD11b/CD18) expression on circulating granulocytes inendurance runners

Purpose: We tested the hypothesis that degranulation of granulocytes and up regulation of the granulocyte integrin MA-1 (CD11b/CD18) are related to exe rcise duration and/or intensity. We also investigated whether or not the ex pression of MAC-1 would be influenced by body temperature or dehydration. M oreover, we tasted the hypothesis that changes in leukocyte counts and chan ges in MAC1 expression with endurance exercise are independently regulated. Methods: In eight amateur runners, MAC-1 (CD11b/CD18) surface expression o n granulocytes was determined by fluorescent antibody cell sorting, before and after an incremental maximal treadmill test, a moderate 3-h run, and a competitive marathon race. Results: Expression CD11b on granulocytes was in creased by 10 +/- 9.6% (P < 0.05) after the maximal treadmill test and by 8 4 +/- 76% (P < 0.01) after the marathon run. There was no change in CD11b e xpression after the moderate 3-h run. CD18 expression was not significantly changed after any of the exercise protocols. Conclusion: Expression of CD1 1b on granulocytes is increased with intense endurance exercise, either inc remental maximal treadmill testing or competitive marathon running, but not in moderate endurance training. Thus, exhaustive exercise may be one mecha nism for the upregulation of Integrin adhesive receptors on granulocytes. T his phenomenon could be in part responsible for increased adhesion of granu locytes to endothelial cells and could facilitate tissue infiltration after endurance exercise.