Amino Acid Balance and Imbalance

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Abstract
The effects of an amino acid imbalance on growth and liver pyridine nucleotide concentrations of rats fed niacin-deficient diets containing 8% of casein have been determined. Growth depressions caused by adding threonine or 6% of gelation to the diet were prevented by niacin supplementation, but those caused by adding 12% of gelatin were not. Liver pyridine nucleotide concentrations were not low even when the growth depression was severe and were unaffected by niacin supplementation. The growth depressions caused by threonine or gelatin were prevented by supplementation of the diet with tryptophan. A supplement of tryptophan caused a rise in liver pyridine nucleotide concentration when the imbalance was caused by threonine, but not when it was caused by gelatin. The conclusion has been drawn from consideration of these results and those of other investigators that imbalances involving niacin and tryptophan are true amino acid imbalances comparable with those demonstrated in diets not deficient in niacin, and that the involvement of niacin is secondary.