AJP - Lung Cellular and Molecular Physiology, Vol 268, Issue 4 539-L545, Copyright © 1995 by American Physiological Society
An age-related difference in hyperoxia lethality: role of lung antioxidant defense mechanisms
A. T. Canada, L. A. Herman and S. L. Young
Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
The role of animal age in the lethal response to > 98% oxygen has been
extensively studied, with the observation that neonatal rats were resistant
while mature animals were sensitive. Antioxidant enzymes increased during
the oxygen exposure in neonatal but not in mature rats, suggesting they
were important in the age-related toxicity difference. Because no studies
had compared the response of mature and old rats to hyperoxia, we exposed
Fischer 344 rats, aged 2 and 27 mo, to > 98% oxygen. Unexpectedly, the
old rats lived significantly longer than young, 114 and 65 h, respectively.
No histopathological differences were found to explain the results. Of the
antioxidants, only glutathione peroxidase (GPx) activity was higher in the
lungs of nonexposed old rats. Superoxide dismutase (SOD) was higher in the
young, results opposite those expected if SOD was important in the
lethality difference. No antioxidant induction occurred in the old
oxygen-exposed rats. These results suggest that although there may be a
role for GPx, mechanisms in addition to antioxidant protection and
inflammation are likely responsible for the age-related difference in
hyperoxia lethality.
