Toxicity and Blood Ammonia Rise Resulting from Intravenous Amino Acid Administration in Man: The Protective Effect of l-Arginine

Abstract

Toxicity and a marked blood ammonia rise were demonstrated in man with intravenous administration of glycine or an L-amino acid mixture free of L-arginine but complete in all the "essential" amino acids. L-Arginine reduced the blood NH3 rise and associated toxicity developing from these amino acid infusions. L-Arginine may be given as a part of the infusion or by intravenous injection immediately or some hours prior to the amino acid infusion. If amino acid administration and the blood NH3 rise are underway, injection of adequate amounts of L-arginine will rapidly reduce the rise. Findings indicate that a functioning metabolic pathway, requiring L-arginine and consistent with the operation of the Krebs-Henseleit cycle, is an important metabolic route when large amounts of amino acids are administered to man. In these circumstances, L-arginine (or a related amino acid) should be regarded as "essential" in the prevention of one aspect of intravenous amino acid toxicity, that of excessive NH3 in the blood.