Superoxide dismutase responds to hyperoxia in rat hippocampus.

The brain's anti-oxidant response to highly elevated oxygen (O2) partial pressures is poorly understood. In this study we hypothesized that hyperbaric O2 (HBO2) would stimulate superoxide dismutase (SOD) transcription in the oxidative stress-sensitive rat hippocampus and measured the time course and extent of the changes in hippocampal mRNA for all three SOD isoforms and total SOD enzyme activity. Comparisons were made between exposures to 2 hours of 1 atmosphere pressure normobaric oxygen (NBO); 2 hours of 3 atmospheres HBO2; and room air. Hyperoxia (HBO2 > NBO) was associated with statistically significant increases in transcript levels of the antioxidant enzymes SOD2 (MnSOD) and SOD3 (EC-SOD) at 6 and 18 hours but not SOD1 (Cu, Zn SOD) respectively. Hyperoxia, however, did not affect total hippocampal SOD activity measured at 6 and 24 hours, indicating that the mRNA responses were necessary to maintain the anti-oxidant enzyme activity after oxidative stress.