Inhibition of superoxide anion release from circulating neutrophils by L-arginine in man

In animal studies of myocardial ischemia/reperfusion L-arginine reduces necrotic injury by preservation of endothelial function and attenuation of neutrophil accumulation in ischemic cardiac tissue. Because release of oxygen radical species by circulating neutrophils is important in endothelial function and ischemia-reperfusion injury, this study investigated the effect of intravenous administration of L-arginine on the in vitro release of superoxide anion of neutrophils in healthy young adults. Neutrophils were obtained at various time points before, during, and after infusion of L-arginine (17 mg kg-1 min-1 for 30 min) and analyzed for superoxide dismutase inhibitable reduction of ferricytochrome c. The spontaneously occurring respiratory burst of polymorphonuclear leukocytes at basal conditions was compared with that after triggering by 1 mumol/l formylpeptide or 50 ng/ml phorbolester. Infusion of L-arginine inhibited both basal (P < 0.01) and formylpeptide-triggered (P < 0.05) release of superoxide anion did, but not affect release stimulated by phorbol 12-myristate 13-acetate. Pretreatment of neutrophils with 1 mmol/l L-arginine in vitro also significantly reduced formylpeptide-triggered (1 mumol/l) superoxide anion release, suggesting that the affects observed after in vivo pretreatment may be due to direct action of L-arginine on neutrophils. These findings demonstrate the ability of L-arginine to reduce release of oxygen radical species by circulating neutrophils in man.