title: Effects of hyperthermic conditions on the reactivity of oxygen radicals.
abstract: Generation and reactivity of superoxide (O2.-) and hydroxyl (OH.) radicals in enzymatic and radiolytic systems were investigated over the temperature range from 20 degrees-50 degrees C. The generation rate and reaction kinetics of both enzymatically and radiolytically produced superoxide radicals were determined by a cytochrome c reduction assay. For OH. radical reaction studies the degradation of hyaluronic acid was assayed. An increase in temperature leads to a greater reactivity of both radicals, but in the case of an enzymatic source a disproportionate increase in the rate of generation is observed. In the pulse radiolysis system, the reactivity of superoxide radicals was found to be stimulated 15-fold over the temperature range from 20 degrees C to 60 degrees C, although the activity of superoxide dismutase was only minimally increased (about 1.6-fold). The results are discussed with respect to the possible importance of active oxygen species to the biological effects of hyperthermia.
authors.affiliation: Gesellschaft fuer Strahlen- und Umweltforschung, Institut fuer Haematologie, Munich, W. Germany.
authors.forename: R D
authors.initials: RD
authors.lastname: Issels
authors.forename: R M
authors.initials: RM
authors.lastname: Fink
authors.forename: E
authors.initials: E
authors.lastname: Lengfelder
mesh_terms: D003574:Cytochrome c Group; D005609:Free Radicals; D006358:Hot Temperature; D006820:Hyaluronic Acid; D006878:Hydroxides; D066298:In Vitro Techniques; D007700:Kinetics; D010084:Oxidation-Reduction; D010100:Oxygen; D013481:Superoxides; D014969:Xanthine Oxidase
chemical_list: D003574:Cytochrome c Group; D005609:Free Radicals; D006878:Hydroxides; D013481:Superoxides; D006820:Hyaluronic Acid; D014969:Xanthine Oxidase; D010100:Oxygen