Effect of Amino Acids on Liver RNA Synthesis in the Chick

Abstract

Two-week-old chicks were administered orally mixtures of vari ous kinds and amounts of amino acids. The effect of these amino acids on RNA synthesis was measured by the incorporation of tritium from uridine-5-3H into RNA of the chick liver. High levels of amino acids (300 mg) administered to chicks resulted in a decrease in RNA synthesis. Of the precursors of the purine ring tested (folie acid, glycine, glutamine and asparuc acid), only aspartA­cacid had any effect on RNA synthesis. It increased the synthesis of RNA. When tested at various levels, 20 mg of aspartic acid per chick promoted the highest amount of RNA synthesis whereas 40 mg of aspartic acid decreased the synthesis of RNA. Amino acid imbalances generally lowered both RNA and protein synthesis when compared to a completely balanced amino acid mixture. Of the imbalances tested by measuring the incorporation of carbon-14 from glycine-l-1'lC into both RNA and protein, a deficiency of tryptophan seemed to have the greatest effect. The data from these experiments in general indicate that amino acids will increase the synthesis of RNA when administered at recommended dietary intakes but will decrease synthesis of RNA when fed at excessively high intakes or as certain unbalanced mixtures. J. Nutr. 102: 987-994, 1972.