Tissue respiration and adenosinetriphosphatase activity in dogs in deep hypothermia

Abstract

The authors studied the intensity of tissue respiration (studied monometrically) and the adenosinetriphosphatase activity (by increase of inorganic phosphorus) in the brain, heart, and skeletal musculature of dogs in deep hypothermia depending on the length of circulatory arrest (30 and 60 minutes) and subsequent warming of the animals to normal temperature. Cooling (to 10° in the mediastinum) and subsequent warming was effected in 10–15 minutes by means of extracorporeal circulation. The tissue respiration and adenosinetriphosphatase activity showed a marked change especially in the brain tissue under the effect of deep hypothermia. Respiratory disturbances of all the tissues investigated were manifested by a reduction of the absorbed O2, and by a drop of the CO2 discharged; the decarboxylation process was disturbed more acutely as seen by the reduced respiratory quotient. A more marked depression of adenosinetriphosphatase activity was revealed in the tissues of cardiac and skeletal muscles following a 60 minute circulatory arrest. After the animals were warmed the tissue respiration and adenosinetriphosphatase activity augmented in all the tissues, indicating that the oxidative metabolic changes in conditions of deep hypothermia were reversible.