FIG. 2.

Cellular compartmentation of GSH and GSSG and metabolism of oxidants. Extracellular, intracellular, mitochondrial, and nuclear compartments are indicated, but other subcompartmental distinctions are not precluded. Although simplified, the schemes shown illustrate the fractal properties of branching in H₂O₂ disposition, as between GPx and other thiol/disulfide-dependent pathways, and Fe-chelate–directed reactions that are not reflected by thiol/disulfide reactions. Also illustrated is that cellular oxidation capacities are based on O₂ and reduction capacities ultimately rely upon food, with NADPH as a key intermediary for any estimates of a global or ‘the’ redox status of a cell. Other concepts to consider are that H₂O₂ could react with Fe²⁺ to form hydroxyl radicals which may lead to lipid peroxides, but perhaps not directly to LOH. DNA (both nuclear and mitochondrial) may also be a target for such radicals. Abbreviations: CoASH, coenzyme A; CoASSG, mixed disulfide of CoASH with GSH; PSH, protein thiol, PSSG, mixed disulfide with GSSG; GPx, glutathione peroxidase; GR, GSSG reductase; ALF, alveolar lining fluid; LOH and LOOH, lipid hydroxy acids and hydroperoxides, respectively.