The influence of hyperbaric oxygen on the function of the adrenal cortex in male rabbits was investigated.
1) Adrenocortical activity shows a diurnal rhythm as evident from the plasma concentration of corticosterone and its metabolites.
The corticosterone level in plasma was maximal in the morning and decreased gradually as the day advanced.
2) The corticosterone level in plasma obtained from a rabbit exposed to 100% O2 at 2kg/cm2 for 10 minutes was higher than that obtained from a rabbit which had been exposed to the same condition for 2hrs daily over a period of 21 days.
3) Adrenal cortex functions did not deteriorate, judging from the result of a 1-24 ACTH test, even after repeated hyperbaric oxygenations.
The results suggest that the adrenal cortex of rabbits adapts to the hyperbaric oxygen condition.
4) The effects of long-term and acute hyperoxia on 2, 3-diphosphoglycerate (2, 3-DPG) in erythrocytes were also studied.
5) The function of the adrenal cortex essentially remained unaffected by the hyperbaric oxygen condition, although the plasma level of corticosterone in the rabbits increased due to hyperoxia.
The results of this study suggest that the clinical application of 1kg/cm2∼2kg/cm2 for 2hrs per day has no significant effect on corticosterone levels in plasma or on the 2, 3-diphosphoglycerate levels in erythrocytes.
