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

Abstract

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.