Abstract
Summary
Fasted male Sprague-Dawley rats (150-200 g) were exposed to 100% oxygen at 5 ATA pressure for 30, 60, and 90 minutes, and ATP concentration, succinic dehydrogenase activity, % free cathepsin activity, % free ribonuclease activity, acid soluble and total nitrogen, and tissue buffer capacity were determined on brain, liver and kidney. ATP concentrations decreased at 30 minutes, returned toward normal at 60 minutes, and showed marked decrease at 90 minutes. Free ribonuclease activity showed an inverse relationship to ATP concentration. This would implicate ATP in the maintenance of lysosome membrane integrity with respect to ribonuclease permeability. Succinic dehydrogenase activity decreased continuously with time of HPO exposure. Free cathepsin activity increased continuously through the 90 minute exposure in brain and liver. Free cathepsin activity increased in kidney through 60 minutes, but at 90 minutes 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 minutes of HPO exposure. This is attributed to hyperventilation by the animal during the HPO exposures. Acid soluble nitrogen was normal at 30 minutes, slightly decreased at 60 minutes and markedly increased at 90 minutes in the 3 tissues. This marked increase during the 60 to 90 minute exposure period coincides with the time interval in which the animals exhibited symptoms of acute hyperoxia toxicity. Significance and implication of the results are discussed.
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