Jan 1, 1975

Factors influencing tolerance of cardiac muscle to hypoxia

Recent Advances in Studies on Cardiac Structure and Metabolism
O H BingW W Brooks


The effects of isoproterenol, glucose, and pH on the responses of isolated rat cardiac muscle to hypoxia (95% N2, 5% CO2) were examined while the muscles were contracting isometrically 12 times a minute at 28 degrees C. In the presence of 5.5 mM glucose, 10(-5) M isoproterenol and alkaline pH (7.8) improved the performance of cardiac muscle during early hypoxia. This was followed by a premature decline in developed tension, and contracture appeared. Recovery of function following reoxygenation with 95% O2 and 5% CO2 after a 60-min period of hypoxia was poor. Acid pH (6.8) resulted in an early decline of mechanical activity during hypoxia; but contracture did not appear, and full recovery of developed tension was seen upon reoxygenation after 60 min of hypoxia. When 22 mM glucose was used as substrate, the early responses to hypoxia were not altered; but late performance was improved, contracture did not appear, and full recovery after 60 min of hypoxia was seen. If additional glucose was added to the bath after 30 min of hypoxia (concentration 22 mM), little effect on developed tension was evident; but contracture diminished and recovery after 60 min of hypoxia was improved. Addition of 22 mM glucose allowed isoproterenol to ex...Continue Reading

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Mentioned in this Paper

Myocardial Contraction
Glucose, (beta-D)-Isomer
Iodoacetic Acids
Drug Augmentation
Heart Diseases
Metabolic Acidosis

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