NITRITE IS PRODUCED BY ELICITED BUT NOT BY CIRCULATING NEUTROPHILS

THE generation of nitrite (NO2-) was used as an index of the productio n of nitric oxide by human and rat polymorphonuclear leukocytes (PMN) and rat peritoneal macrophages. Human peripheral blood PMN did not pro duce significant levels of NO2-. Attempts to induce NO2- generation in human PMN by incubation with GM-CSF (1nM), TNF alpha (0.3 nM), endoto xin (1 mu g/ml) or formyl-Met-Leu-Phe (100nM) for up to 16h were not s uccessful. Addition of human PMN primed by GM-CSF (1nM) to rabbit aort ic ring preparations precontracted with phenylephtine had no effect on tone. In contrast to these observations, PMN, isolated from the perit oneum of oyster glycogen treated rats, generated NO2 via a pathway sen sitive to inhibition by the nitric oxide synthase inhibitor, N-G-monom ethyl L-arginine. However, peripheral blood rat PMN obtained from the same animals did not produce NO2-, even during prolonged incubation fo r periods of up to 16 h. It is suggested that detectable NO production by PMN requires NO synthase activity to be induced either by the proc ess of PMN migration or by exposure to certain cytokines produced loca lly at the site of inflammation.