Effects of hypoxia and hypocapnia on brain redox balance in ducks.
Low arterial CO2 tension (PaCO2) experienced by birds during high-altitude flight may result in cerebral vasoconstriction with reduced cerebral O2 delivery. To test this, brain redox balance and blood volume were studied during severe hypocapnia (PaCO2 11-20 mmHg) in ducks. Cerebrocortical redox balance, measured as relative [NADH], and blood volume were measured simultaneously with a fiber-optic fluorometer-reflectometer. Cerebrocortical blood volume (an index of blood flow) fell nearly linearly with PaCO2 during severe hypocapnia, even during severe hypoxemia. Cerebrocortical redox balance was shifted toward reduction of NADH ([NADH] increased) by both hypoxemia and hypocapnia. If hypocapnia causes similar changes in brain blood flow during high-altitude flight, tissue hypoxia will be exacerbated. Tolerance of brain tissue hypoxia during flight may be an important adaptation in high-flying birds.
Bickler
P E
PE
Anesthesia Department, University of California, San Francisco 94143-0542.
Koh
S O
SO
Severinghaus
J W
JW
D000818:Animals; D001810:Blood Volume; D001921:Brain / Q000378:metabolism*; D002245:Carbon Dioxide / Q000097:blood*; D002560:Cerebrovascular Circulation; D004372:Ducks / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D009243:NAD / Q000032:analysis; D010084:Oxidation-Reduction
D009243:NAD; D002245:Carbon Dioxide