Chemiluminescence probe with Cypridina luciferin analog, 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2- a]pyrazin-3-one, for estimating the ability of human granulocytes to generate O 2−

Abstract

The Cypridina luciferin analog, 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2- a]pyrazin-3-one (CLA), in Hanks' balanced salt solution, emitted a weak luminescence which was not affected by superoxide dismutase or catalase and was not augmented by resting human granulocytes. In contrast, activated granulocytes caused a dramatic increase in the luminescence of CLA. The light emission by CLA in the presence of activated granulocytes was inhibited by superoxide dismutase, but not by catalase or benzoate. Azide at 0.5 m m did not inhibit light emission significantly. These results indicate that O 2 −, rather than H 2O 2, HO·, singlet oxygen, or HOCl, was the agent responsible for eliciting the chemiluminescence of CLA. Moreover, the intensity of light emission by CLA correlated with the rate of production of O 2 − either by activated neutrophils or by the xanthine oxidase reaction.