Effect of Acute Hypoxia on Ascorbate Content of Plasma, Cerebral Cortex, and Adrenal Gland

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Abstract
Levels of ascorbic acid (AA) in the plasma, brain and adrenal gland of rats were determined after 15 min of hypoxia (PaO2 < 25 mm Hg) and followed asphyxia. In rabbits, AA plasma levels were followed up to 75 min of reoxygenation following 15 min of hypoxia of the same severity. A significant increase (.apprx. 70%) in AA levels was found in plasma of rats and rabbits after hypoxia and asphyxia. This increase was found to be transient, with a return to normal levels within 1 h after resumption of normal oxygenation. Pretreatment with dexamethasone reduced the increase in AA level in both rabbits and rats. Adrenalectomy in rats, performed 24 h before the experiment, abolished the response to hypoxia. Ascorbate levels in the cerebral cortex, hypothalamus and adrenal gland of awake rats subjected to hypoxia or asphyxia were found to be the same as in normoxic rats. The observed changes in plasma AA levels are probably mediated through ACTH and the adrenal gland apparently is the major source of ascorbate efflux into the circulation during O2 deprivation.