RESUMO
AIM: To study the effects of morphine on active oxygen free radicals. METHOD: Chemiluminescence method was used to measure (a) active oxygen generation induced by respiratory burst of neutrophils from human blood stimulated with phorbol myristate acetate (PMA), (b) Superoxide anion (O2.-) induced by xanthine-xanthine oxidase system, (c) hydroxyl radical (.OH) generated by ascorbic acid (AA)-Cu(2+)-zymosan, and (d) the release of H2O2. RESULTS: The (a), (b), (c), and (d) were scavenged by morphine and their median inhibitory concentrations (IC50 and 95% confidence limits) were 21.1 (13.0-34.0), 54.1 (50.0-58.5), 224.0 (128.2-390.8), and 66.9 (62.9-71.0), nmol L-1, respectively. CONCLUSION: The immunosuppressant effect of morphine was related to its free radicals scavenging action.