Amino Acid Imbalance as Related to Methionine, Isoleucine, Threonine and Tryptophan Requirement of the Rat or Mouse

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Abstract
Growth of weanling rats was depressed more than 50% when oxidized casein was added to a diet containing peanut meal as a protein source. This growth depression (or imbalance) could be corrected by additions to the diet of methionine or, under certain conditions, of vitamin B12. The addition of hemoglobin to a corn grain diet produced an imbalance that was corrected by supplements of isoleucine. The supplementation of certain amino acids to a casein diet produced a marked reduction in growth. Threonine supplements, however, prevented the depression in growth. The amino acid imbalances increased the amount of food required per gram of gain in body weight of the animals. This was corrected by supplementation of the diet with the corresponding amino acids. Plasma levels of methionine were not altered by the methionine imbalance. Tryptophan deficiency, however, caused a reduction in plasma amino acids. The survival of adult rats fed protein-free diets was not influenced by supplements of certain amino acid-deficient proteins, glycine or urea. An amino acid imbalance was produced in weanling mice fed a casein-oxidized casein diet. This imbalance could be largely prevented by supplements of tryptophan to the diet.