[Effect of experimental starvation on the age-related characteristics of phenylalanine metabolism]

Experiments with administration of phenylalanine were made to study its content in the blood and urine of young and old intact rabbits, as well as under the starvation-simulated restriction of protein synthesis. The old animals manifested an increased rate of phenylalanine increment, and of its excretion with the urine, apart from the reduced tyrosine biosynthesis. Starvation counteracts the age-associated differences as regards the body response to phenylalanine administration, with a tendency towards more distinctive shifts being seen in the young animals. It is concluded that with age the rate of assimilation and hydroxylation of phenylalanine diminishes and the possibilities of its use to meet tyrosine requirements get restricted. It is recommended that amino acids and protein supply be restricted during aging.