Studies on amino acid levels and transport in the mechanically stressed rat heart

Two types of experiments were performed to evaluate the role of amino acids in the early phase of cardiac hypertrophy in the rat. In one series of experiments the intracellular concentration of free amino acids was measured in both sham-operated rats and rats which had undergone aortic constriction. At both 18 and 48 h after surgery all the essential amino acids measured and the majority of the nonessential amino acids were present at the same concentration in both hypertrophying and nonhypertrophying heart muscle. In a second series of experiments the capacity of the perfused rat heart to concentrate [14C]AIB was compared between hearts subjected to a maximal work load and nonworking preparations. No difference in [14C]AIB uptake was found between working and nonworking preparations. These data suggest that primary changes in amino acid transport and intracellular levels do not occur in acute cardiac hypertrophy and that the hypertrophy process is characterized by a coordinated increase in both muscle mass and amino acid content.