Myocardial Metabolism V. Effect of Puromycin on Protein Synthesis and Oxidation of Glucose,Acetate,and Aspartate in Perfused Rat Hearts 1

Summary

The recirculation with 0.46 mM puromycin in Krebs bicarbonate buffer containing 9 mM glucose had no effect on the myocardial uptake of leucine-1-¹⁴C, but depressed leucine incorporation into protein from 55 to 2%. The rate of myocardial contraction and coronary flow were unaffected. Myocardial removal of glucose from the medium was increased from 70 μmoles/hr to 114 μmoles/hr, and the oxidation of glucose to ¹⁴C0₂ was increased from 8 to 24 μmoles/hr. To eliminate glycolysis as a site of puromycin action, similar studies were carried out with perfusions of 10 mM acetate. As in the case of glucose perfusion, the circulation of puromycin stimulated acetate uptake from 100 to 128 μmoles and increased acetate oxidation from 42 to 58 μmoles. Since the data suggested an effect of puromycin on mitochondrial Krebs cycle activity, labeled aspartate was perfused in the presence of acetate and puromycin. There was a 20% increase in uptake and a 30% increase in the oxidation of aspartate due to puromycin perfusion. However, there was no change in the levels of endogenous aspartate. The results suggest that puromycin affects mitochondrial oxidative pathways, either directly or via an effect on mitochondrial permeability and oxidative phosphorylation.