Synthesis of ethanolamine phosphoglycerides in rat cerebral cortex subjected in vitro to experimental hypoxia with and without hypocapnia.

Slices and homogenates from rat cerebral cortex were used to study the effect of hypoxia, with or without hypocapnia, on phosphatidylethanolamine synthesis. The incorporation of [1-3H]ethanolamine into the corresponding phospholipid was greatest in slices treated with pure nitrogen, intermediate when the nitrogen contained 5% CO2, and least in slices treated with 95% O2-5% CO2. The role of hypocapnia in reinforcing the effect due to hypoxia did not require the integrity of the cell because similar results were obtained by treating homogenates with pure nitrogen or nitrogen plus 5% CO2. In both cases the synthesis of phosphatidylethanolamine was abolished by the addition of EGTA and the degradation of newly synthesized phospholipid by phospholipases was similar to that obtained in controls. When the homogenate was not buffered, changes in the pH due to experimental treatment influenced the response to Ca2+ and to hypoxia plus hypocapnia. Intracellular calcium ions are thought to play a role in the response of cerebrocortical slices to N2-treatment. In fact, although the incorporation was greater in complete medium that contains 2 mM Ca2+ than in the same medium prepared without the addition of this ion, the relative increase of incorporation due to N2-treatment was greater in the medium lacking added Ca2+.