Acclimatization to hypoxia modulates the tryptophan 2,3-dioxygenase activity in rats exposed to simulated high altitude.
1. Exposure of rats to an 8000 m altitude increased the hepatic tryptophan 2,3-dioxygenase (EC 1.13.1.12) activity. 2. Acclimatization to hypoxia by a repeated exposure to an altitude of 5000 m induced a marked decrease in liver tryptophan dioxygenase activity after the rats were subjected to an 8000 m altitude, but a pre-exposure to 4000 m altitude showed no effect on the enzyme activity. 3. Plasma tryptophan was rapidly decreased by exposure to 8000 m altitude to the same extent in the acclimatized and non-acclimatized rats. 4. Plasma tryptophan may be utilized as the substrate for tryptophan dioxygenase in liver of the non-acclimatized rats under highly hypoxic conditions; however, acclimatized rats can reserve tryptophan as the substrate for the alternative metabolism other than the degradation pathway in liver.
Yoshino
M
M
Department of Genetics, Institute for Developmental Research, Aichi Prefectural Colony, Japan.
Mori
S
S
Nakatsuka
M
M
Shibata
Y
Y
D000064:Acclimatization / Q000502:physiology; D000531:Altitude; D000818:Animals; D000860:Hypoxia / Q000097:blood / Q000201:enzymology*; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D008099:Liver / Q000201:enzymology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014364:Tryptophan / Q000097:blood; D014366:Tryptophan Oxygenase / Q000378:metabolism*
D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D014364:Tryptophan; D014366:Tryptophan Oxygenase