Evidence for the participation of superoxide anion radical in altering the adhesive interaction between granulocytes and endothelium, in vivo.

The aim of this study was to characterize granulocyte behaviour, in venules, after enzymatic generation of free radicals on the surface of the hamster cheek pouch and to elucidate the role of superoxide anion radical (O2-), H2O2 and hydroxyl radical in these changes. A decrease in granulocyte velocity, which was dissociated from a concomitant increase in red cell velocity, was found while granulocyte rolling frequency and granulocyte adhesion increased in the venules studied. These alterations in granulocyte behaviour could be completely inhibited by superoxide dismutase, an enzymatic scavenger of O2-, but not by catalase, which decomposes H2O2 or by L-methionine which may scavenge OH. and quench singlet O2. Our results are consistent with the concept than an O2-dependent lipid hydroperoxide generated on the hamster cheek pouch by the xanthine oxidase system markedly alters granulocyte behaviour in vivo.