Effects of oxygen deprivation on incorporation of [U- 14C]-glucose into macromolecules of guinea pig cerebral cortex slices

Abstract

Incorporation of [U- 14C]-glucose into lipid, protein, RNA and DNA of guinea pig brain cortex slices was studied in vitro for varying time intervals under conditions of anoxia and recovery from anoxia. In addition, pH values ranging from 6.8 to 8.0 were also studied to examine their effect on postanoxic cellular metabolism. The following observations were made: (i) Maximal incorporation of [U- 14C]-glucose into macromolecules of slices was observed during 15 min of anaerobic incubation; longer incubation produced no further uptake. (ii) Following incubation under anaerobic conditions for 15 min, slices regained the capacity to incorporate glucose radiocarbon into macromolecules when transferred to an oxygenated incubation medium, but exhibited lower rates than those of controls which were not exposed to anoxia. While protein synthesis showed significant recovery immediately after anoxia, no further incorporation occurred following an initial period of uptake. The same was true for protein synthesis after increased intervals of anaerobic preincubation. However, the rates of incorporation into DNA and RNA were not significantly affected. Synthesis of lipid was maintained at the highest level of all molecular classes studied. (iii) Studies at different pH values showed that 7.4 was the optimum pH for incorporation. (iv) High concentration of unlabelled glucose in the incubation medium greatly improved postanoxic recovery. In conclusion, exposure to anoxic conditions irreversibly inhibited further protein synthesizing activity in brain slices after an initial constant increment of residual synthesis, while synthesis of nucleic acids and lipid were reversible, albeit depressed.