Time course and quantitative analysis of the adaptive responses to 85% oxygen in the rat lung and heart

The phenomenon of oxygen tolerance (resistance to 100% O-2 in rats previous ly exposed to 85% O-2) constitutes one of the few models of adaptive respon ses to oxidative stress in mammals. In vitro studies suggest that reactive oxygen species mediate this response. To test this hypothesis in vivo, we f ollowed the time course of oxidative stress, enzyme induction, and edema in the lung, heart and liver of rats exposed to 85% O-2 for 1 to 5 days. Inte restingly, not only the lung, but also the heart of rats exposed to 85% O-2 showed increases in the production of O-2(.-) (aconitase inactivation) ear ly during the exposure. Increases in O-2(bullet-) were associated to oxidat ive stress (increased in situ chemiluminescence) and transient edema in bot h tissues. Both the lung and heart displayed induction of superoxide dismut ase and reversion of the oxidative stress and damage. The adaptive response in the heart was faster and more efficient, suggesting that this tissue is at a more critical risk when exposed to elevated O-2 concentrations. (C) 2 000 Elsevier Science B.V. All rights reserved.