Glutathione, reduced

The quantitative analysis for reduced glutathione in blood is complicated by the presence of many potential interferents. 

The FAD-dependent enzyme glutathione reductase plays a role in the antioxidant system. Glutathione reductase restores reduced glutathione (GSH), the most important antioxidant in erythrocytes, from oxidized glutathione (GSSG) [1, 2]. 

The glutathione (GSH) level was assayed by the method of Sedlak and Lindsay (ref. 14), using Ellman s reagent (5,5-dithio-bis-(2-nitrobenzoic acid). Calibration was carried out parallely to each series, using reduced glutathione as a standard. 

Glutathione-S-transferases A group of enzymes that catalyze the formation of conjugates between reduced glutathione and xenobiotics. 

Figure 20-3. Role of the pentose phosphate pathway in the glutathione peroxidase reaction of erythrocytes. (G-S-S-G, oxidized glutathione G-SH, reduced glutathione Se, selenium cofactor.)...

Figure 45-6. Interaction and synergism between antioxidant systems operating in the lipid phase (membranes) of the cell and the aqueous phase (cytosol). (R-,free radical PUFA-00-, peroxyl free radical of polyunsaturated fatty acid in membrane phospholipid PUFA-OOH, hydroperoxy polyunsaturated fatty acid in membrane phospholipid released as hydroperoxy free fatty acid into cytosol by the action of phospholipase Aj PUFA-OH, hydroxy polyunsaturated fatty acid TocOH, vitamin E (a-tocopherol) TocO, free radical of a-tocopherol Se, selenium GSH, reduced glutathione GS-SG, oxidized glutathione, which is returned to the reduced state after reaction with NADPH catalyzed by glutathione reductase PUFA-H, polyunsaturated fatty acid.)...

Reduced glutathione (GSH) is important in the metabolism of the RBC, in part to counteract the action of potentially toxic peroxides the RBC can synthesize GSH and requires NADPH to return oxidized glutathione (G-S-S-G) to the reduced state. 

Figure 4.9 Effect of reduced glutathione (GSH) (0.25-1.0 ihm) and oxidized glutathione (GSSG) (0.25-1.0 mM) on ouabain-sensitive Na/K ATPase activity. An isolated Na/K ATPase preparation was prepared from fresh bovine ventricular tissue. Na/K ATPase activity was determined and quantified by the ouabain-sensitive hydrolysis of ATP to yield Inorganic phosphate. The rate of inorganic phosphate production was compared prior to and following the addition of either GSH or GSSG to the Incubation mixture. The data are presented as...

Figure 4.14 Diagrammatic representation of (a) oxy-radical>mediated S-thioiation and (b) thiol/disulphide-initiated S-thiolation of protein suiphydryl groups. Under both circumstances mixed disuiphides are formed between glutathione and protein thiois iocated on the ion-translocator protein resulting in an alteration of protein structure and function. Both of these mechanisms are completely reversible by the addition of a suitabie reducing agent, such as reduced glutathione, returning the protein to its native form.

Garcia Ruiz, C., Fernandez Checa, J. and Kaplowitz, N. (1992). Bidirectional mechanism of plasma membrane transport of reduced glutathione in intact rat hepatocytes and membrane vesicles. J. Biol. Chem. 267, 2256-2264. 

The GSH reductase inhibitor l,3-bis(2-chloroethyl)-l-nitrosourea (BCNU) also promotes corneal swelling in the isolated cornea. The addition of GSH prevents the action of BCNU as the cornea needs a constant supply of NADPH for maintaining adequate concentrations of reduced glutathione for the detoxification of hydrogen peroxide. It has been shown that hydrogen peroxide and BCNU primarily affect the permeability of the endothelial cells rather than the active processes transporting sodium and chloride ions across the membrane (Riley, 1985). 

GSHPx, CAT and SOD, which normally protect cells from free-radical damage have not been detected in aqueous humour. It has therefore been su ested that damage by free radicals and hydrogen peroxide to the anterior segment is prevented by a non-enzymatic extracellular oxidoreduction system involving a constant supply of reduced glutathione to the aqueous fluid from the ciliary epithelium, cornea and lens (Riley, 1983). 

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