ACTIVE OXYGEN SPECIES IN THE LIVER OF RATS SUBMITTED TO CHRONIC HYPOBARIC HYPOXIA

The spontaneous in situ liver chemiluminescence of female rats submitt ed to 4,400 m (simulated altitude) for 2 mo and of their corresponding controls at sea level was determined as an approach to the measuremen t of the intracellular steady-state concentrations of singlet oxygen a nd oxygen free radicals. Spontaneous liver chemiluminescence was decre ased by approximately 40% in hypoxic rats, whereas CCl4-induced chemil uminescence was unchanged. Liver mitochondria isolated from hypoxic ra ts showed a 53% decreased rate of H2O2 production and an increased con tent of cytochrome b (36%), with normal content of cytochromes c1, c, and a-a3. Superoxide dismutase showed a 26% decrease in activity, wher eas catalase and glutathione peroxidase activities were not significan tly decreased by this extent of hypoxia. Cytochrome P-450 and glutathi one contents were unchanged. There were no significant differences in the hydroperoxide-initiated chemiluminescence (an estimation of tissue chain-breaker antioxidants) of homogenates, mitochondria, and microso mes. Results suggest that in chronic hypoxia there is a lower rate of generation of active oxygen species in liver, leading to a decreased s teady-state concentration of singlet oxygen.