Total parenteral nutrition with selective histidine depletion in man I. Responses in nitrogen metabolism and related areas

Abstract

To test whether histidine is an essential on dispensable amino acid, a normal adult man received nutrients by intravenous alimentation for 48 days during an overall 72-day experiment. After control periods, a 3-day lysine-free intake caused a marked negative nitrogen balance. Deletion of histidine for 27 days resulted in a close to zero corrected nitrogen balance. Omission of histidine did not significantly affect serum urea, uric acid, or creatinine, although urea and uric acid were higher and lower, respectively, in the continuous intravenous periods than in the postabsorptive oral periods. During the absence of histidine, eight serum proteins (total protein, albumin, prothrombin, alkaline phosphatase, lactic dehydrogenase, glutamate-oxaloacetate transaminase, glutamate-pyruvate transaminase, and ornithine transcarbamylase) remained essentially constant and in the normal range for 27 days. Decreases in plasma and urinary histidine to low stable concentrations were observed during histidine omission. Changes in the other specific plasma and urinary amino acids reflected the intravenous intake. Indices of function for the liver, pancreas, and muscle were not detectably changed by the histidine-free intake. Although the above observations are the statistically significant ones, the possibility remains that several measurements, reflecting very gradual changes, might be modified with a histidine-free intake longer than 27 days, or with an experiment with additional volunteer subjects. These and other findings must be considered in the evaluation of the need for histidine in normal man.