Effect of anoxia and hypoxia on brain lipid metabolism.

Lipid metabolism in rat brain was investigated in mild hypoxia (5-7% O2 in nitrogen), which is associated with no apparent change in energy metabolism, and in severe anoxic conditions (ischemic anoxia), which are associated with a rapid decrease in ATP and oxygen content in brain. When brain slices were incubated with labeled glucose or acetate, the amount of labeled CO2 produced was no different in experimental and control conditions, but the incorporation of radioactivity into brain lipids was decreased in all hypoxic and anoxic conditions. Interestingly, the incorporation of label from [14C]glucose into phosphatidylinositols was specifically inhibited by both hypoxic conditions but not by conditions associated with anoxia. The incorporation of the same labeled precursor, i.e., [14C]glucose, into fatty acids was elevated in ischemic anoxia but reduced after mild hypoxia. Because of the obvious differences in oxygen utilization in brain in anoxic and hypoxic conditions, we believe that the observed disturbances in lipid metabolism may be due to factors other than those that arise from oxygen deficiency alone.