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Further Studies on Amino Acid Imbalance Produced by Gelatin in Rats on Niacin-Tryptophan Low Ration¹

Three Figures

Department of Biochemistry, College of Agriculture, University of Wisconsin, Madison

The influence of 6% gelatin in creating an amino acid imbalance in the rat receiving a 9% casein-dextrin diet has been reported.

If no supplemental L-cystine or DL-methionine were added to the diet of animals receiving the gelatin, only slight growth inhibition was noted. Addition of L-cystine or DL-methionine produced a severe growth inhibition, curable with 1.5 mg % of niacin.

Fed in conjunction with a given carbohydrate, L-cystine did not alter cecal niacin levels, so improved growth in the absence of L-cystine was not due to changes in the intestinal flora. Improved growth on the dextrin diet was considered to be a result of increased synthesis of niacin by the intestinal bacteria.

The combination of L-proline, DL-threonine, DL-phenylalanine, glycine, L-arginine and DL-alanine, in the presence of L-cystine, was the most effective in producing the growth inhibition and deficiency symptoms analogous to those induced by gelatin. DL-Alanine seemed to be necessary, for in its absence no symptoms were observed.

The increased growth on the low casein-dextrin diet and the limiting nature of L-cystine and DL-methionine in the diet, which induced a cystine deficiency before the tryptophan became the limiting amino acid, were attributed to failure to produce the amino acid imbalance syndrome in the absence of supplemental sulfur amino acids.

We are indebted to Merck and Co., Inc., Rahway, N. J., for the crystalline vitamins; to the Lederle Laboratories Division, American Cyanamid Co., Pearl River, N. Y., for synthetic folic acid; to Abbott Laboratories, North Chicago, Ill., for haliver oil; and to Wilson and Co., Inc., Chicago, Ill., for the gelatin.

Manuscript received 9 April 1951.