Some effects of hypoxia on respiratory metabolism and protein synthesis in rat tissues

Abstract

Nembutalized rats were pump ventilated with 5% oxygen-95% nitrogen for periods of 60 or 105 min. Samples of liver, kidney, and brain obtained at the end of the period of hypoxia were used for ATP determinations and for polarographic measurements of respiration, respiratory control, and oxidative phosphorylation. In some experiments, leucine-C¹⁴ was injected intravenously after 60 min of hypoxia, and tissue uptake and incorporation of leucine into protein determined after an additional 45-min period of hypoxia. After 105 min of hypoxia, brain ATP was reduced 20%, liver ATP 40%, and kidney ATP was unchanged. The incorporation of leucine-C¹⁴ into protein was moderately depressed in brain and kidney and almost completely abolished in liver. The polarographic studies indicated that the capacity of tissue homogenates for basal and ADP-stimulated respiration and for oxidative phosphorylation was not impaired by 60 or 105 min of severe hypoxia. It is concluded that the damaging effects of hypoxia, of the severity and duration studied, are due mainly to the reduction in tissue ATP levels rather than to damage of the ATP-producing system.