Increase in extracellular glutathione peroxidase in plasma and lungs of mice exposed to hyperoxia

Extracellular glutathione peroxidase (E-GPx) is a selenium-dependent enzyme that can reduce hydrogen peroxide and phospholipid hydroperoxides. E-GPx i s found in plasma and extracellular fluids such as bronchoalveolar lavage f luid. Because lung is one of the tissues that is capable of synthesizing an d secreting E-GPx, the effect of exposure to hyperoxia on E-GPx in plasma a nd lung were studied in an injury model of hyperoxia exposure in adult mice . Exposure to 100% oxygen for 72 h resulted in an increase of 55% in plasma GPx activity and an increase of 50% in the amount of E-GPx protein in the plasma. Exposure to hyperoxia was also associated with an increase in the a mount of E-GPx protein in lungs. The 7-fold increase in the amount of E-GPx protein in lungs was not due to plasma contamination of lungs from mice ex posed to hyperoxia. E-GPx in the lung is calculated to account for 10% of l ung GPx activity in control mice. However, E-GPx is calculated to account f or 45% of lung GPx activity in the lungs of mice exposed to hyperoxia for 7 2 h. Further studies are needed to determine whether the increase in lung E -GPx is due to changes in translation or stability of E-GPx. The role of E- GPx in protecting the lung from oxidative damage warrants further study.