15N-Studies in Severe Renal Failure II. Evidence for the Essentiality of Histidine

Abstract

Urea containing heavy nitrogen was given intravenously to two uraemic patients. Essential amino acids were administered daily by mouth or intravenously. Protein from muscle samples and plasma protein was hydrolyzed. ¹⁵N-excess in the isolated amino acid nitrogen was determined. ¹⁵N was recovered in all the amino acids except in threonine, lysine, and histidine. The results were compared with those from a patient in severe post-traumatic catabolism. In this case, and in a previously studied healthy volunteer, ¹⁵N was recovered also in histidine from muscle and plasma protein. This difference in ¹⁵N-distribution between the uraemic patients, and the healthy subject and the patient in post-traumatic catabolism, supports the hypothesis that histidine is an amino acid which is essential in severe uraemia.