Effect of hyperbaric oxygen treatment and perfluorochemical administration on glutathione status of the lung

Exposure to hyperoxia, especially under hyperbaric conditions, causes an enhanced oxidative stress particularly in lung tissue. To test the potential hazardous effect of either a single or repeated hyperbaric oxygen treatment (HBO) on the cellular defence system the glutathione status of lung tissue from rats exposed to HBO was investigated. When daily exposed to 2.5 ATA of > 95% O2 for 90 min over 8 or 14 days the content of reduced glutathione in lung tissue (GSH) increased by 16-19%. Oxidized glutathione (GSSG) tended to increase after 8 days and was 56% higher after 14 days. While the GSSG/GSH ratio was unchanged after 8 days, it increased by 39% after 14 days. Thus, the GSH increase after 8 days can be understood as a adaptive process to protect the lung from oxidative stress. The distinct increment of the cellular GSSG that lead to an increase of the GSSG/GSH ratio after 14 days reflects a situation, in which the cellular defence system is overwhelmed by oxidative stress. The additional pretreatment with perfluorochemicals in a dose of 2g/kg every second day aggravated the observed changes (GSH +39-19%, GSSG +118%). In a second experiment rats were exposed to a single session with 7 ATA of O2 for 60 min. GSH in the lungs increased for 40%, it was not elevated by PFC. However, GSSG increased to a much higher degree in untreated as well as in PFC-treated animals (+240%, +163%), elevating the ratio GSSG/GSH markedly (+145%, +176%). Allopurinol given as radical scavenger in a dose of 50 mg/kg was able to suppress the increased oxidative stress widely. Thus adaptive and overloading processes are involved under the treatment with increased oxygen pressures. As the administration of PFC aggravates the observed changes, a still increased blood oxygen offer must be considered as the causative agent. A radical scavenger is capable to suppress the increased oxidative stress widely.