INFLUENCE OF NITRIC-OXIDE ON LUMINOL-ENHANCED CHEMILUMINESCENCE MEASURED FROM PORCINE-STIMULATED LEUKOCYTES

The influence of endogenous nitric oxide (NO) and NO-releasing compoun ds on free radical release from porcine leukocytes was in investigated by luminol-enhanced chemiluminescence (CL). The direct free radical-s cavenging activity of the compounds was determined by a cell-free syst em using xanthine plus xanthine oxidase (X+XO). The NO donor, N-(2-hyd roxyethyl)nicotinamide nitrate (nicorandil), markedly inhibited CL gen erated by phorbol myristate acetate (PMA)-stimulated leukocytes. In ad dition, nicorandil and S-nitrozo-N-acetylpenicillamine (SNAP) both dec reased CL generated by X+XO. Conversely, C87 3754, a NO-releasing sydn onimine, decreased free radical release from leukocytes only when prei ncubated with the cells and had no effects on the X+XO system. None of the NO donors inhibited peroxynitrite-generated CL. L-, but not D-, a rginine inhibited PMA-activated free radical generation without affect ing X+XO-induced CL. L-Canavanine, N-omega-nitro-L-arginine (L-NNA), a nd L-nitro-arginine methyl ester (L-NAME), inhibitors of the NO pathwa y, augmented PMA-induced CL. However, L-canavanine, but not L-NNA and L-NAME, produced a significant inhibition of X+XO-induced CL. It is co ncluded that endogenous NO may play an important role in the measureme nt of free radicals released from porcine leukocytes, assessed by lumi nol-enhanced CL, and that compounds with NO-releasing properties decre ase CL, possibly by interfering with free radical generation.