The Effect of Some Amino Acids on the Growth and Nicotinic Acid Storage of Rats on Low Casein Diets*

Krehl et al. (1, 2) have observed that the inclusion of large amounts of corn grits in a low protein diet produced a growth retardation in rats, which was corrected by the addition of either nicot,inic acid or L-tryptophan. The beneficial action of the amino acid is now attributed to its role as a biological precursor of nicotinic acid (3-5). It is not necessary to postulate the existence of a specific pellagragenic agent in corn for the rat, at least, because the deficiency syndrome with corn can be duplicated n-it’h non-corn rations by the addit,ion of tryptophan-deficient proteins or acid-hydrolyzed proteins to a nicotinic acid-deficient diet containing suboptimal amounts of tryptophan (6). Inasmuch as nicotinic acid produced normal growth on the nicotinic acid-deficient diets only when these protein supplements were present, it appears probable t.hat the unsupplemented diet, was also inadequate with regard to some amino acids. In this respect, Hall and Sydenstricker (7) have observed normal growth in rats when lysine, valinc, threonine, histidinc, and tryptophan \vere added to low casein diets adequate in other respects. We report here the production of a severe nicotinic acid deficiency in the rat on low protein diets supplemented with some amino acids and the cffcct. of these subst,ances on the storage of nicotinic acid in the liver.