Systemic hypoxia promotes leukocyte-endothelial adherence via reactive oxidant generation.

We recently demonstrated that systemic hypoxia during reduced inspired PO(2) produces a rapid increase in leukocyte adherence to rat mesenteric venules. Evidence suggests that the mechanism of this response involves decreased nitric oxide (NO) levels. One possible pathway for NO depletion could involve increased reactive oxygen species (ROS) generation resulting in inactivation of NO. The overall goal of the present study was to examine the role of ROS in promoting leukocyte-endothelial adherence during systemic hypoxia. Experiments were designed to 1) evaluate changes in ROS generation in the mesenteric microcirculation during systemic hypoxia, 2) determine how the ROS signal changes when PO(2) levels return to normal after a period of systemic hypoxia, 3) assess the effect of antioxidants on ROS generation during hypoxia, and 4) utilize antioxidants to examine the functional relationship between ROS generation and leukocyte adherence during hypoxia. The major findings from this study are that systemic hypoxia increases ROS generation within the mesenteric microcirculation and that antioxidants prevent the increase in leukocyte-endothelial adhesive interactions observed in hypoxia.