title: The relative effectiveness of .OH, H2O2, O2-, and reducing free radicals in causing damage to biomembranes. A study of radiation damage to erythrocyte ghosts using selective free radical scavengers.
abstract: The relative effectiveness of oxidizing (.OH, H2O2), ambivalent (O2-) and reducing free radicals (e- and CO2-) in causing damage to membranes and membrane=bound glyceraldehyde-3-phosphate dehydrogenase of resealed erythrocyte ghosts has been determined. The rates of damage to membrane-bound glyceraldehyde-3-phosphate dehydrogenase (R(enz)) were measured and the rates of damage to membranes (R(mb)) were assessed by measuring changes in permeability of the resealed ghosts to the relatively low molecular weight substrates of glyceraldehyde-3-phosphate dehydrogenase. Each radical was selectively isolated from the mixture produced during gamma-irradiation, using appropriate mixtures of scavengers such as catalase, superoxide dismutase and formate. .OH, O2- and H2O2 were approximately equally effective in inactivating membrane-bound glyceraldehyde-3-phosphate dehydrogenase, while e- and CO2- were the least effective. R(enz) values of O2- and H2O2 were 10-times and of .OH 15-times that of e-. R(mb) values were quite similar for e- and H2O2 (about twice that of O2-), while that of .OH was 3-times that of O2-. Hence, with respect to R(mb): .OH greater than e- = H2O2 greater than O2-, and with respect to R(enz): .OH greater than O2- = H2O2 much greater than e-. The difference between the effectiveness of the most damaging and the least damaging free radicals was more than 10-fold greater in damage to the enzyme than to the membranes. Comparison between H2O2 added as a chemical reagent and H2O2 formed by irradiation showed that membranes and membrane-bound glyceraldehyde-3-phosphate dehydrogenase were relatively inert to reagent H2O2 but markedly susceptible to the latter.
mesh_terms: D002374:Catalase / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D004307:Dose-Response Relationship, Radiation; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D004912:Erythrocytes / Q000378:metabolism*; D005609:Free Radicals; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000097:blood; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D006878:Hydroxides / Q000494:pharmacology*; D017665:Hydroxyl Radical; D007700:Kinetics; D010100:Oxygen / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000494:pharmacology*
chemical_list: D005609:Free Radicals; D006878:Hydroxides; D013481:Superoxides; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D010100:Oxygen