Elevated Plasma Phenylalanine Concentration and Lysine Incorporation Into Ribosomal Protein of Developing Brain

Hyperphenylalaninemia was induced in 7‐day‐old rabbits over a 6‐hr period by intraperitoneal injection of phenylalanine. l ‐[U‐ 14 C]Lysine was injected intraperitoneally into these rabbits and into a control group. The rate of incorporation of l ‐[U‐ 14 C]lysme into brain ribosomal protein was decreased during a 5‐hr period in the presence of elevated plasma phenylalanine concentrations. Lysine transport from the peritoneum to the plasma was unaffected by the high plasma phenylalanine concentrations.