Although a close relationship exists among carbohydrate, protein, and amino acid metabolim, the study of synthesis and degradation of amino acids in heart muscle has been an almost neglected subject. The proposed research is based on two recent observations: (1) clinical studies in patients with and without coronary artery disease have indicated that amino acids can be either released or utilized by the human myocardium; and (2) in vitro studies of an isolated heart muscle preparation have demonstrated de novo synthesis of alanine and utilization of glutamic acid by hypoxic heart muscle. The proposed studies encompass three major objectives: (a) to identify the source of alanine and to clarify any potential correlation between glycolysis and breakdown of branched chain amino acids to alanine synthesis and release; (b) to search for other amino acids or their metabolites as end products of hypoxic myocardial metabolism; and (c) to learn about nitrogen metabolism (release of ammonia and urea) in the normal and oxygen-deprived myocardium. These studies will contribute to our knowledge of hypoxic myocardial cell damage. A more detailed understanding of metabolic derangements caused by diminished myocardial oxygen supply should in turn contribute to the important clinical problem of diminishing or reversing the effects of myocardial oxygen deprivation.