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 poo l of leukocytes that can be mobilized by exercise or catecholamines. This s tudy was designed to determine the phenotypic characteristics of leukocytes that are mobilized into the circulation during exercise. Twenty healthy vo lunteers performed incremental exercise to exhaustion [maximal O-2 consumpt ion (VO2max)] on a cycle ergometer. Blood was collected at baseline, at S-m in intervals during exercise, at VO2max, and 30 min after exercise. Total w hite cell, polymorphonuclear leukocyte (PMN), and lymphocyte counts increas ed 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 b aseline 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 1 0.2 +/- 0.6 at baseline to 25 +/- 2.5 at VO2max, P < 0.002) but remained un changed on lymphocytes. Myeloperoxidase levels in PMN did not change with e xercise. In vitro studies showed that neither catecholamines nor plasma col lected at VO2max during exercise changed leukocyte L-selectin or CD11b leve ls. We conclude that PMN released from the marginated pool during exercise express low levels of L-selectin and high levels of CD11b.