Effects of ouabain on cerebral metabolism during anoxia

Abstract

Ouabain at low concentration such as 10 μM greatly enhances the rate of anaerobic glycolysis in adult rat as well as guinea pig cerebral cortex slices incubated in a calcium free Locke bicarbonate medium. The enhancing effect of ouabain on the rate of anaerobic glycolysis is significantly reduced in the presence of Ca2+. Ouabain has no effect on the anaerobic glycolysis of 2 days old rat brain or acetone powder extracts of adult brain or on the aerobic glycolysis of cerebral cortex slices. During anoxia, the Na+ and K+ contents of the cerebral cortex slices are unaffected by ouabain. However, an increase in the ATP contents of incubated cerebral cortex slices is observed. It is concluded that the enhancement of the rate of anaerobic glycolysis of cerebral cortex slices by ouabain is presumably due to a rise in the cell ATP concentration as a result of inhibition of Na+, K+ ATPase which exerts a rate limiting effect on the sugar phosphorylation. The diminished effect of ouabain on the rate of anaerobic anerobic glycolysis, in the presence of Ca2+, may be due to change in the accessibility of Na+, K+ ATPase to ouabain.