Effects of Hyperbaric Oxygenation on Metabolism. IV. Time Sequence of Biochemical Changes at 5 Atmospheres 100% Oxygen.

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Abstract
Fasted male Sprague-Dawley rats (150-200 g) were exposed to 100% O2 at 5 atm. pressure for 30, 60, and 90 min., and ATP concentration, succinic dehydrogenase activity, percent free cathepsin activity, percent free RNase activity, acid soluble and total N, and tissue buffer capacity were determiaei on brain, liver and kidney. ATP concentrations decreased at 30 min., returned toward normal at 60 min., and showed marked decrease at 90 min. Free RNase activity showed an inverse relationship to ATP concentration. This would implicate ATP in the maintenance of lysosome membrane integrity with respect to RNase permeability. Succinic dehydrogenase activity decreased continuously with time of hyperbaric oxygenation [HPO] exposure. Free cathepsin activity increased continuously through the 90-min. exposure in brain and liver. Free cathepsin activity increased in kidney through 60 min., but at 90 min. showed a decrease which is attributed to a marked decrease in both free and total cathepsin activity at this time. Tissue buffer capacity in all 3 tissues showed a decrease in tissue acidity at 30, 60, and 90 min. of HPO exposure. This is attributed to hyperventilation by the animal during the HPO exposures. Acid soluble N was normal at 30 min., slightly decreased at 60 min. and markedly increased at 90 min. in the 3 tissues. This marked increase during the 60 to 90-min. exposure period coincides with the time interval in which the animals exhibited symptoms of acute hyper-oxiatoxicity. Significance and implication of the results are discussed.

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