AJP - Endocrinology and Metabolism, Vol 247, Issue 4 475-E482, Copyright © 1984 by American Physiological Society
Cerebral oxygen and energy metabolism during and after 30 minutes of moderate hypoxia
D. Kintner, J. H. Fitzpatrick Jr, J. A. Louie and D. D. Gilboe
Sixty-four isolated canine brain preparations were subjected to either 15
or 30 min of perfusion with blood equilibrated at either Pao2 30 mmHg or
Pao2 40 mmHg followed by up to 60 min of reoxygenation with blood having a
Pao2 greater than 100 mmHg. Pao2 30 mmHg perfusion decreased oxygen
availability and the cerebral metabolic rate for oxygen (CMRo2) to 44 and
49% of normal, respectively, whereas Pao2 40 mmHg perfusion decreased
oxygen availability and CMRo2 to 64 and 70% of normal, respectively.
Creatine phosphate was markedly decreased (0.6 and 4% of normal,
respectively) and ATP was only slightly decreased (73 and 90% of normal,
respectively) in these preparations during the hypoxic period. Although ATP
returned to normal during the reoxygenation period in both groups, creatine
phosphate and CMRo2 returned to normal only in the Pao2 40 mmHg
preparations. In brains perfused at various Pao2 levels for periods ranging
from 6 to 30 min, the total oxygen deficit (the cumulative difference over
time between normal and actual CMRo2) rather than tissue lactate levels
appeared to influence the restoration of CMRo2 to normal following hypoxia.
An oxygen deficit in excess of 25 mumol/g precluded return to a normal
CMRo2 following reoxygenation.(ABSTRACT TRUNCATED AT 250 WORDS)
