Brain energy metabolism in hypoxemia.

The relationship of various levels of arterial and cerebral venous Po2to the cerebral energy state was evaluated in rats exposed to a lowering of the arterial Po2to 40, 30, and 20 mm Hg, respectively. The arterial Po2and cercbral venous Po2could be reduced down to 20 and 10 mm Hg, respectively, without major derangement of the cerebral energy state. Determinations of glycolytic and Krebs cycle substrates revealed clear evidence of an increased glycolytic flux occurring in the absence of any major changes in the adenine nucleotides. It is concluded that the present theories concerning the relationship of cerebral venous Po2to tissue oxygenation are inadequate.

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