Role of superoxide anion radicals in microvascular permeability and leukocyte behaviour

Inflammation is associated with the accumulation and activation of phagocytic cells, such as polymorphonuclear leukocytes, and with the subsequent release and generation of a group of activated oxygen species, some of which are free radicals. These studies were carried out to assess the influence of enzymatically generated free radicals on both microvascular permeability and leukocyte adhesion. The extravasation of fluorescein-labelled dextran mean molecular weight (MW) 150 000 was used to assess microvascular permeability and methodology was developed to measure in vivo leukocyte endothelial interactions. Enzymatically generated superoxide anion radical (O-.2) was associated with an increase in macromolecular extravasation (seen primarily from postcapillary venules) and an increase in leukocyte adhesion. Macromolecular extravasation was found to be dependent on the generation of a hydroxyl radical related interaction while leukocyte adhesion was dependent on the presence of O-.2. It is suggested that the permeability alterations and increased polymorphonuclear leukocyte adhesion seen during inflammation may be partially related to the release of free radicals from inflammatory cells.