Lucigenin Is a Mediator of Cytochrome C Reduction but Not of Superoxide Production

The relevance of lucigenin (bis-N-methylacridinium nitrate)-amplified chemiluminescence (CL) as a specific assay for superoxide ion has recently been disputed (S. I. Liochev and I. Fridovich, Arch. Biochem. Biophys. 337, 115–120, 1997). These authors suggested that the redox cycling of lucigenin can...

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Bibliographic Details
Published in:Archives of biochemistry and biophysics 1999-06, Vol.366 (2), p.267-274
Main Authors: Afanas'ev, Igor B., Ostrachovitch, Elena A., Korkina, Ludmila G.
Format: Article
Language:English
Subjects:
Acridines - chemistry
Acridines - metabolism
Animals
Cattle
chemiluminescence
cytochrome c
Cytochrome c Group - chemistry
Cytochrome c Group - metabolism
Hydrogen-Ion Concentration
lucigenin
Luminescent Measurements
NAD - metabolism
Oxidation-Reduction
superoxide
Superoxides - chemistry
Superoxides - metabolism
Xanthine - metabolism
Xanthine Oxidase - metabolism
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Summary:The relevance of lucigenin (bis-N-methylacridinium nitrate)-amplified chemiluminescence (CL) as a specific assay for superoxide ion has recently been disputed (S. I. Liochev and I. Fridovich, Arch. Biochem. Biophys. 337, 115–120, 1997). These authors suggested that the redox cycling of lucigenin can lead to the formation of additional amount of superoxide ion. However, thermodynamic consideration shows that the equilibrium for the reaction O•−2 + Luc2+ ⇔ O2 + Luc•+ is completely shifted to the right (Keq = 106); therefore, the redox cycling of lucigenin is of no importance. This conclusion is supported by the study of the effects of lucigenin on cytochrome c reduction by xanthine oxidase. It was found that lucigenin did enhance the rate of cytochrome c reduction with xanthine as a substrate, but it did not increase the rate of xanthine oxidation. When NADH was used as a substrate, lucigenin inhibited the SOD-dependent component of cytochrome c reduction and enhanced both the SOD-independent cytochrome c reduction and NADH oxidation, being a sole acceptor of an electron from the enzyme. All these findings indicate the extremely low probability of lucigenin redox cycling. In our opinion, lucigenin-amplified CL remains the most sensitive and highly specific test for superoxide formation in biological systems.
ISSN:0003-9861
1096-0384
DOI:10.1006/abbi.1999.1215