Effects of inhibitors on chicken polymorphonuclear leukocyte oxygenation activity measured by use of selective chemiluminigenic substrates

Chicken heterophil polymorphonuclear leukocytes (CPMNLs) have NADPH oxidase activity, but lack myeloperoxidase (MPO). Stimulation of CPMNLs by phorbol 12-myristate 13-acetate or chicken opsonified zymosan results in luminol-d ependent chemiluminescence (CL) activity, which is small relative to that o f human peroxidase-positive neutrophils (HPMNLs), as well as lucigenin-depe ndent CL, comparable to HPMNL responses. Inhibitors were used to investigat e and characterize the CL activity of CPMNLs, Inhibition constants were cal culated, using Dixon inhibition analysis, or were reported as the concentra tion producing 50% inhibition of the magnitude of CL responses. Azide and cyanide are effective inhibitors of luminol CL in HPMNLs, althoug h these peroxidase inhibitors do not inhibit either luminol or lucigenin CL of CPMNLs, Since these agents also inhibit eosinophil peroxidase, lack of inhibition of CPMNL CL indicates that the small percentages of peroxidase-p ositive eosinophils in CPMNL preparations are not responsible for the lumin ol CL observed. Iodoacetate and fluoride, pre-oxidase and pre-peroxidase in hibitors of glycolytic metabolism, effectively inhibit lucigenin and lumino l CL activities in CPMNLs. Superoxide dismutase competitively inhibits luci genin and luminol CL in CPMNLs, but catalase is an ineffective inhibitor. A lthough luminol is efficiently dioxygenated by a MPO-dependent mechanism in HPMNL, use of peroxidase-deficient CPMNLs indicates that this substrate do es not exclusively measure peroxidase activity.