Ryan and Carver1 reported that injections of phenylalanine (L-phenylalanine) into rabbits and rats inhibited their synthesis of diphtheria antitoxin in response to diphtheria toxoid. Later, Ryan2 found that phenylalanine and one of its metabolites, phenethylanine, inhibited formation of antibody in rats injected with sheep erythrocytes. Furthermore, Ryan reported that administration of phenylalanine in very large doses was accompanied by prolongation of survival of allogeneic skin grafts between mice of certain different inbred strains from a range of 9.5 to 10.5 days to a range of 15 to 16 days.
The present experiments were performed to study the effects of administration of large doses of phenylalanine in rabbits, repeating and extending the work of Ryan and Carver,1 and to determine the effect of phenylalanine on survival of allografts of skin in rabbits and of kidneys in dogs.
The concentration of phenylalanine in serum of rabbits