Effects of Severe Systemic Hypoxia on Myocardial Energy Metabolism

By the use of freeze‐clamp technique, simultaneous tissue samples were taken from the right atrial and the right ventricular muscle of the working heart in anesthetized dogs during a hypoxia‐recovery cycle consisting of 4 min of severe, systemic hypoxia followed by a period of recovery of equal duration. In order to study the energy metabolism of the two parts of the heart, the tissue samples were analyzed with respect to their content of creatinephosphate, adenine nucleotides, pyruvate, lactate, dihydroxyacetonephosphate, α‐glycerophosphate and malate. During aerobic, controlled ventilation, the ventricular tissue was found to contain higher concentrations of high‐energy phosphate compounds than the atrial tissue. During the period of hypoxia, the atrial and ventricular tissue contents of creatinephosphate were reduced to about 10% whereas ATP was reduced merely to about 70% of the control values. The rate of the anaerobic glycolysis was found to proceed more rapidly in the ventricular muscle, thereby indicating a higher rate of energy metabolism, than in the atrial muscle.