Cerebral Bioenergetics and in Vivo Cytochrome c Oxidase Redox Relationships
Cytochrome c oxidase (cytochrome a,a3) is almost completely oxidized in isolated mitochondria1 which essentially respire at a maximal rate. The reduction level of cytochrome a,a 3 measured in intact brain and other mammalian organs, however, is much higher2,3. The in vivo oxidation-reduction level of this enzyme is also greatly affected by variations in tissue oxygenation4. Cytochrome a,a 3 becomes progressively more reduced by pathophysiological conditions which decrease cellular oxygen availability5. Thus, in situ changes in the oxidation level of cytochrome a,a 3 should provide an early sensitive means for determining intracellular levels of oxygen insufficiency which adversely affect tissue bioenergetics. We test this possibility in the present study. The effect of acute oxygen insufficiency on in stu changes in the oxidation level of cytochrome a,a 3 in the parietal cortex of skull intact normal blood circulated rat brain was directly compared with in vitro measured changes in the concentration of metabolites known to reflect limitations in cellular energy production.
KeywordsParietal Cortex Inspire Oxygen Oxidation Level Fractional Content Hemoglobin Saturation
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