Luminol-dependent chemiluminescence (CL) of human polymorphonuclear neutrophils (PMN) phagocytosing opsonized zymosan (OPZ) was studied. CL occurred immediately after addition of OPZ to PMN suspension, reached its peak in 15-20 min. and decreased gradually thereafter. The intensity of the peak CL was proportional to the number of PMN and the concentration of luminol. Increased amount of OPZ resulted in a shortened interval before the peak CL; its intensity, however, was not affected significantly by the amount investigated. Experiments using inhibitors of oxygen radicals such as superoxide dismutase, catalase, sodium benzoate, histidine and sodium azide revealed that histidine and sodium azide were most potent, which might suggest a direct perticipation in the emission of CL by singlet molecular oxygen generated in the myeloperoxidase-mediated reactions. CL emmited by PMN phagocytosing OPZ is easy to measure, and appears to reflect phagocytosis and killing action of PMN and also opsonic potential of the substance used to opso-nized zymosan if normal PMN are employed.
