Influence of Gelatin on Growth and Liver Pyridine Nucleotide Concentration of the Rat

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Abstract
Growth and liver pyridine nucleotide concentrations (NAD-NADP) of rats fed a 6% casein, niacin-deficient basal diet supplemented with either 12% of gelatin or a mixture of indispensable or dispensable amino acids simulating the amino acid composition of 12% of gelatin were determined. Growth was significantly depressed by these supplements below that obtained for rats fed the basal diet. Tryptophan prevented the growth depression caused by gelatin or the mixture of indispensable amino acids, but not that due to the mixture of dispensable amino acids. The liver NAD-NADP of rats fed the diets that were not supplemented with tryptophan were not markedly different. A tryptophan supplement significantly increased the liver NAD-NADP of rats fed the basal diet or the diet containing the mixture of indispensable amino acids, but produced only small increases in rats fed the diets containing gelatin or the mixture of dispensable amino acids. By feeding rats diets containing various combinations of the dispensable amino acids in the quantities in which they occur in 12% of gelatin, glycine or L-4-hydroxyproline were shown to be responsible for both the growth depression, and the decreased synthesis of liver NAD-NADP in response to a supplement of tryptophan. Rats fed diets containing gelatin did not show a decreased ability to synthesize NAD-NADP when large amounts of tryptophan were injected, nor did gelatin appear to interfere with the induction of tryptophan pyrrolase.