Regulation of Protein Synthesis in Heart Muscle

Abstract

Abstract Perfusion of the isolated rat heart under anaerobic conditions inhibited synthesis of whole heart protein and myosin. The effect was reversible and did not appear to be due to the decrease in mechanical activity. Anaerobic inhibition of protein synthesis appeared to be due to a block in incorporation of free amino acids from the intracellular pool into protein rather than a block in the entry of amino acids into the cell. Intracellular levels of amino acids were either unchanged or increased in the anaerobic heart with exception of aspartic and glutamic acids. Entry of aspartic acid, isoleucine, and phenylalanine into the cell was unchanged by anoxia, whereas entry of glycine, aminoisobutyric acid, and lysine was accelerated. Inhibition of protein synthesis was associated with somewhat fewer ribosomal subunits and more polysomes than found in aerobic hearts perfused under the same conditions. A 50% reduction in GTP and a 3-fold increase in GMP was found in the anaerobic heart.