De-acclimatization process of rats acclimatized to high altitude hypoxia.

The de-acclimatization process in rats acclimatized to high altitude hypoxia was analyzed according to the changes in the activities of hepatic enzymes. The activities of tryptophan 2,3-dioxygenase and tyrosine aminotransferase in the liver of non-acclimatized rats were increased, whereas those of acclimatized rats were decreased after exposure to a simulated altitude of 8,000 m. When the acclimatized rats were kept under normoxic conditions for 8 days and over, the suppression of enzyme induction was nullified, and both enzymes were induced by exposure to the simulated 8,000 m altitude. De-acclimatization of rats acclimatized to hypoxia can be completed in 8-11 days.