MODULATION BY SUPEROXIDE ANIONS OF NEUTROPHIL-MEDIATED PLATELET ACTIVATION

When polymorphonuclear neutrophil-platelet suspensions were stimulated by 0.5 mu M N-formyl-Met-Leu-Phe in the presence of 40 U/mL of supero xide dismutase, a significant reduction of platelet secretion was obse rved (51.4 +/- 6.3% vs 62.4 +/- 4.6% for control; mean +/- SEM; N = 6; P < 0.01). This was due to the superoxide anion scavenging property o f superoxide dismutase since neutrophil degranulation, cathepsin G and elastase enzymatic activities (the two main mediators of this cell-to -cell interaction) and platelet reactivity were not affected. Involvem ent of superoxide anions was confirmed using leukotriene B-4, a neutro phil agonist which induces degranulation with minimal superoxide anion production. Indeed, serotonin release induced by this agonist was unc hanged whether superoxide dismutase was added or not.