Expression of the cell adhesion molecules on leukocytes that demarginate during acute maximal exercise

The pulmonary vascular bed is an important reservoir for the marginated pool of leukocytes that can be mobilized by exercise or catecholamines. This study was designed to determine the phenotypic characteristics of leukocytes that are mobilized into the circulation during exercise. Twenty healthy volunteers performed incremental exercise to exhaustion [maximal O-2 consumption (VO2max)] on a cycle ergometer. Blood was collected at baseline, at S-min intervals during exercise, at VO2max, and 30 min after exercise. Total white cell, polymorphonuclear leukocyte (PMN), and lymphocyte counts increased with exercise to VO2max (P < 0.05). Flow cytometric analysis showed that the mean fluorescence intensity of L-selectin on PMN (from 14.9 +/- 1 at baseline to 9.5 +/- 1.6 at VO2max, P < 0.05) and lymphocytes (from 11.7 +/- 1.2 at baseline to 8 +/- 0.8 at VO2max, P < 0.05) decreased with exercise. Mean fluorescence intensity of CD11b on PMN increased with exercise (from 10.2 +/- 0.6 at baseline to 25 +/- 2.5 at VO2max, P < 0.002) but remained unchanged on lymphocytes. Myeloperoxidase levels in PMN did not change with exercise. In vitro studies showed that neither catecholamines nor plasma collected at VO2max during exercise changed leukocyte L-selectin or CD11b levels. We conclude that PMN released from the marginated pool during exercise express low levels of L-selectin and high levels of CD11b.