Sodium superoxide, decomposition

The precise mechanism by which NO causes glutamase neurotoxicity is unknown. Calcium must be required because of the requirement for NMDA- and glutamate-induced NO formation in brain tissue (Garthwaite etal., 1988). Although both NMDA-receptor agonists and sodium nitroprusside induce specific neurotoxicity as well as cyclic GMP formation in brain tissue (Dawson et al., 1991), it is unlikely that cyclic GMP is the ultimate cause of the neurotoxicity. Instead, NO is most likely involved in producing target cell death. One possible mechanistic pathway is that locally synthesized NO and superoxide anion react with each other to yield peroxynitrite anion (Beckman et al., 1990), which can destroy cell membranes either directly via interaction with cellular thiols (Radi et al., 1991) or indirectly via decomposition to hydroxyl and other free radicals (Beckman et al., 1990). 

Figure 3. Decomposition of dHG in buffered media in the presence of a) catalase (1,700 U/ml), superoxide dismutase (SOD) (1700 U/ml) plus thiourea (1.0 mM), or SOD (1700 U/ml) plus benzoate (1.0 mM) b) ascorbic acid, (1.0 mM), reduced gluthathione (1.0 mM), thiourea (1.0 mM), or sodium benzoate (1.0 mM) c) phenylthiocarbamide (1.0 mM), or 2,4-Dithiopyrimidine d) diethylenetriaminepentaacetic acid (DTPA) (1.0 mM), ethylenediaminetetraacetic acid (EDTA) (1.0 mM), or no chelator.

Rosen (1977) has presented evidence that formation of hypochlorus acid by the MPO-H2O2-CI system generates 2 in an identical manner to the reaction of H2O2 in sodium hypochlorite. Peters (1972) has shown potassium peroxychromate to liberate 02 upon decomposition while Khan (1970) has shown the evolution of 02 from potassium superoxide in dimethyl-sulfoxide. Spectral evaluation of these CL sources revealed filter transmission patterns similar to the CL produced by phagocytozing PMN and MNL s and that produced by H2O2 oxidation reactions. 

After the first steps in the area of electrochemistry towards the end of nineteenth century, the beginning of twentieth century brought increased activity of Czech chemists. The mysterious electrolytic silver superoxide still attracted attention of V. Novak, O. Sulc, J. Baborovsky (1875-1946) (Fig. 3.1.2), and B. Kuzma (1873-1943) [4, 5]. Experiments to determine the voltage of anodic decomposition of sodium hydroxide were carried out by F. Plzak (1877-1944). The papers on the abovementioned topics were published in Czech or in German. 

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