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Quantitative nutritional studies with water-soluble, chemically defined diets. III. Individual amino acids as sources of “non-essential” nitrogen

1957; Elsevier BV; Volume: 72; Issue: 2 Linguagem: Inglês

10.1016/0003-9861(57)90218-7

1096-0384

Sanford M. Birnbaum, Milton Winitz, Jesse P. Greenstein,

Clinical Nutrition and Gastroenterology

The basal diet described earlier, and consisting of the ten "essential" amino acids to 9.5 g. total N, B-vitamins, ascorbic acid, salts, and glucose was dissolved in water to 50% concentration and offered to weanling male rats. Over a 21-day period there was an average weight gain of 9 g. or about 0.45 g. per day per animal. Various amino acids and other nitrogenous compounds were individually added to the basal diet at the expense of an equal amount of the glucose component, and the resulting diets, also in 50% aqueous solution, were likewise offered ad libitum to weanling rats. These supplemented diets were all isonitrogenous, i.e., either 25.2 or 22.0 g. total N/kg. The diets providing the best growth, about 3 g. per day, were those in which l-alanine, ammonium l-glutamate, l-glutamine, ammonium l-aspartate, and l-proline were individually furnished as the sole source of "non-essential" nitrogen. The additions of the d-isomers of alanine and of arginine to the basal diet accelerated growth but not to the same extent as that produced by the corresponding l-isomers when also employed singly. Ammonium acetate proved more effective in promoting growth than either urea or glycine, while l-serine, l-hydroxyproline, and l-cysteine, at the levels used (15.7 g. total N/kg. diet) proved to be toxic to the animals.