Regulation of thiols in the brain. 2. Effect of hypozia on the activities of cytoplasmic NADPH-producing enzymes in different parts of the rat brain

Activities of cytoplasmic NADPH-producing enzymes were determined in cerebral grey matter, midbrain, cerebellum and the brain stem of the rat. Mild hypoxia affected the activities of glucose 6-phosphate dehydrogenase (G6PD) and of malate dehydrogenase: G6PD activity progressively increased for 2 h and malate dehydrogenase decreased after I h. The ability of cerebral tissue to produce the four NADPHproducing enzymes, changed parallel to the changes in amount of thiols previously observed during the same degree of hypoxia. Increases of G6PD activity together with previously postulated accumulation of oxidized glutathione during hypoxia strongly suggest stimulation of the hexose monophosphate shunt in the brain by lowered oxygen supply.