Changes in oxidative stress and vascular reactivity of thoracic and abdominal rat aorta with different periods of exposure to hyperbaric oxygenation

Oxidative stress and the antioxidant defense always seek balance in aerobic systems. Therefore, when O₂ is added to an aerobic system during hyperbaric oxygenation, oxidative stress is induced and the antioxidant defense is stimulated. Dose-response curves were established for rat aorta exposed to different agonists. The aorta were from control rats and animals with 3, 10 or 20 HBO sessions. Parameters of vascular reactivity, oxidative stress and antioxidant defense were measured. With hyperbaric oxygenation, vascular reactivity was modified by the altered interaction between oxidative stress and antioxidant defense. The result was a low contractile response, possibly caused by endothelium dependent or independent pathways. Since, acetylcholine did not modify the vascular response, HBO seems to act by endothelium independent pathways related to nitric oxide. Hyperbaric oxygen therapy (HBO) led to an over 60% decrease in all parameters of oxidative stress and antioxidant defense (enzymatic and non-enzymatic) of thoracic aorta, an effect that lasted during the 20 sessions of HBO. This result indicates a probable drastic reduction in ROS and NO production, which could be explained by the capacity of an excess of oxygen to eliminate certain products that are normally involved in chain reactions leading to oxidative stress.