OXIDATIVE STRESS DECREASES ANTIOXIDANT ENZYME-ACTIVITIES IN REAGGREGATION CULTURES OF RAT-BRAIN CELLS

The brain has been suggested to be especially sensitive to damage by r eactive oxygen species. In this study, we examined the effects of hype roxic conditions on the activities and mRNA levels of antioxidant enzy mes in reaggregation cultures of rat forebrain cells. Cultures were ex posed to 80% oxygen for 12-60 h starting on Days 17 and 33 in culture. Superoxide dismutase activities and mRNA levels were not affected by hyperoxia, whereas catalase activity was slightly decreased after 24 h in 80% oxygen at Day 17. Glutathione peroxidase activity was markedly decreased already after 12 h of hyperoxia, and decreased activities o f glutathione reductase and glucose-6-phosphate dehydrogenase were als o noted. The glutathione peroxidase mRNA levels were increased in hype roxic cultures at Day 17 but not at Day 33. These results suggest that the enzymatic defense mechanisms against reactive oxygen species in t he brain are rather weak and deteriorate during oxidative stress but t hat a potential for compensatory upregulation exists at least during t he first postnatal weeks.