Effects of long-term oxygen treatment on [alpha]-ketoglutarate dehydrogenase activity and oxidative modifications in mitochondria of the guinea pig heart

Objective Oxygen therapy is used for the treatment of various diseases, but prolonged exposure to high concentrations of O.sub.2 is also associated with formation of free radicals and oxidative damage. Methods In the present study we compared [alpha]-ketoglutarate dehydrogenase (KGDH) activity and mitochondrial oxidative damage in the hearts of guinea pigs after long-term (17 and 60 h) oxygenation with 100% normobaric O.sub.2 and with partially negatively (O.sub.2 neg) or positively (O.sub.2 posit) ionized oxygen. Results Inhalation of O.sub.2 led to significant loss in KGDH activity and thiol group content and accumulation of bityrosines. Inhalation of O.sub.2 neg was accompanied by more pronounced KGDH inhibition, possibly due to additional formation of protein-lipid conjugates. In contrast, O.sub.2 posit prevented loss in KGDH activity and diminished mitochondrial oxidative damage. Conclusions These findings suggest that oxygen treatment is associated with impairment of heart energy metabolism and support the view that inhalation of O.sub.2 posit optimizes the beneficial effects of oxygen therapy. Keywords: oxygenation, reactive oxygen species, [alpha]-ketoglutarate dehydrogenase, heart, oxidative damage