Some Specific Effects of Hypobaric Hypoxia on Cellular Metabolism

The lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activity of mouse liver homogenates were examined after exposure to an equivalent altitude of 36,000 feet and compared to controls kept at ground level. After 6 and 12 hour incubation periods, the altitude exposed samples demonstrated a significantly higher LDH activity than controls. SDH activity remained unchanged from controls after 6 hours but was significantly lower than controls after 12 hour exposures to altitude. It is concluded that the changes in enzyme activity reflect a metabolic control mechanism to maintain adequate energy production during periods of exposure to hypobaric hypoxic stress.