Hyperbaric oxygen(HBO) therapy for carbon monoxide(CO) poisoning eventually inducing the hypoxia-reoxygenation condition, may produce oxygen free radicals, which forms 8-hydroxydeoxyguanosine(8-OH-dG) by attacking C-8 position of deoxy-guanosine (dG) in DNA. Effects of oxygen partial pressure or duration of HBO therapy with or without CO poisoning on the tissue 8-OH-dG formation were investigated. Male Sprague-Dawley rats were grouped and exposed to air(control group), 4000ppm of CO for 10 to 30 minutes(CO only group), air for 30 minutes after 30 minute exposure to 4000ppm of CO(CO-air exposure group), HBO after 30 minute exposure to 4000ppm of CO(CO-HBO group), or HBO therapy for 10-120 minutes (HBO only group). The 8-OH-dG concentrations in the brain and the lung tissues were measured with high performance liquid chromatography and electrochemical detector (ECD). Average concentrations of the 8-OH-dG of each group were statistically compared. In the brain tissues, 8-OH-dG concentrations of the CO only group, the CO-air exposure group, and the CO-HBO group did not significantly differ from those of the control group. Similar insignificance was also found between the CO-HBO group and the HBO only groups. No appreciable dose-response relationship was observed between the 8-OH-dG concentration and the oxygen partial pressure or the duration of HBO. However, the 8-OH-dG concentrations of the 30 minute CO only group were higher than those of the CO-air exposure group (p-value<0.05). In the lung tissues, there were no significant differences between the 8-OH-dG concentrations of the control group and those of the CO only group, the CO-air exposure group, and the CO-HBO group. However, mean 8-OH-dG concentration of the CO-air exposure group was significantly higher than that of the CO only group under the same CO exposure condition(p-value<0.05). With the duration of CO exposure, the 8-OH-dG concentrations of the lung tissues decreased significantly (p-value<0.05). The concentrations of 8-OH-dG in the lung tissues proportionally increased with the duration of HBO, but no such relation was observed with the oxygen partial pressure. These results suggest that the brain may be more resistant to oxygen free radicals as compared with the lungs, and that oxygen toxicity following HBO may be affected by factors other than oxygen free radicals.
Since the widespread application of hyperbaric oxygenation in clinical medicine, the problems of oxygen toxicity have been attracting a deep interest from the researchers on hyperbaric medicine as a practical issue. Among extensive research trials, the study on the protective agents oxygen toxicity occupied one of the most challenging field. As the mechanisms of oxygen toxicity, the role of the oxygen free radicals produced by peroxidation process are strongly accepted by the leading researchers on oxygen toxicity, the probable protective effects of antioxidant against oxygen toxicity are sustaining a sufficient rational. Maltol(2-methyl-3-hydroxy-gamma-pyrone) which is known to be a component of Korean red ginseng has been reporting to have an antioxidant action. But, further study is needed to provide definite evidence for this compound to be an antioxidant, since the action was based on the results which were obtained under in vitro experiment. In this study, the author attempted to evaluate the effect of maltol as protective agent against oxygen toxicity through the observation of death rate, convulsion rate, time to convulsion and microscopic pathological changes in some organs of experimental rats exposed to various conditions. The findings observed are as follows: 1) The death rate, convulsion rate, time to convulsion, lung/weight ratio and microscopic pathological finding of lung were identified as reliable objective and quantitative indices for oxygen toxicity. 2) Maltol showed excellent protective effect against pulmonary oxygen toxicity as an antioxidant.