Hyperphenylalanemia: effect on brain polyribosomes can be partially reversed by other amino acids

The effect of a single injection of phenylalanine (2 mg/g of body weight) on brain polyribosomes, which increases the number of inactive monoribosomes, persists for 2 to 3 hours. A single injection of seven large neutral amino acids after phenylalanine administration results in a reversal of the effect on brain polyribosomes with a resultant decrease in monoribosomes to near normal levels. The other common amino acids are apparently not limiting during hyperphenylalanemia, because an injection of these did not increase recovery.