Reversible ischemia of the brain: biochemical factors influencing restitution.

Biochemical factors of potential importance for the development of irreversible brain cell damage in reversible ischemia may, at least theoretically, not only involve anaerobic events but also oxidative reactions. If so, such reactions should be expected to occur either if oxygen delivery to the tissue during ischemia is not totally abolished, i.e. as in incomplete ischemia, or during the recirculation phase. Several investigations have shown that pronounced incomplete brain ischemia is more deleterious than complete ischemia. The persistence of some circulation in the former situation may a) allow oxidative reactions to continue at a slow rate b) lead to excessive tissue lactic acidosis by continued supply of substrate for anaerobic glycolysis. Our studies concerning brain tissue concentrations of reduced and oxidized glutathione, fatty acids and phospholipids in reversible, pronounced, incomplete and complete ischemia fail to support the hypothesis that oxidative damage is an important factor for the development of irreversible neuronal damage. On the other hand, our studies have shown that the degree to which lactate accumulates during ischemia is critical for restitution.