CHEMILUMINESCENCE IN THE OXIDATION OF 6-HYDROXYDOPAMINE: EFFECTS OF LUCIGENIN, SCAVENGERS OF ACTIVE OXYGEN, METAL CHELATORS AND THE PRESENCE OF OXYGEN |
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Authors: | Dolores J Fatur † Richard H C San † Allan J Davison † Hans F Stich † |
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Institution: | Bioenergetics Research Laboratory, Simon Fraser University, B.C. V5A 1S6 and Environmental Carcinogenesis Unit, B.C. Cancer Research Centre, 601 West 10th Avenue, Vancouver B.C. V5Z 1L3, Canada |
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Abstract: | Abstract— Maximum chemiluminescence in a system containing 6-hydroxydopamine (6-OHDA) and H2O2 required the addition of Fe2+:EDTA, oxygen, and lucigenin. In this system luminescence was strongly inhibited by catalase (91% inhibition) or 50 m M mannitol (83%), whereas superoxide dismutase or ascorbate did not significantly change the reaction rate. In the absence of lucigenin, 50 m M mannitol (78%), catalase (76%), or ascorbate (73%) inhibited strongly, while superoxide dismutase inhibited by 60%. Removing EDTA from the lucigenin-containing system caused a 79% decrease in luminescence, while the substitution of desferoxamine for EDTA decreased luminescence by 55%. In the presence of desferoxamine plus EDTA the luminescence increased by 30% in comparison with that seen with EDTA alone. Luminescence in the system containing 6-hydroxydopamine, H2O2, Fe2+:EDTA and lucigenin required the presence of oxygen (93% inhibition anaerobically), consistent with a mechanism involving reductive oxygenation of the lucigenin. It is concluded that luminescence in the presence of lucigenin involves a substantial contribution from H2O2 and Fe2+ mediated by a mannitol-sensitive intermediate (conceivably Fenton-derived hydroxyl radicals). In the absence of lucigenin, superoxide and an ascorbate-labile component are additional important participants in the process. |
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