FREE AMINO ACIDS OF SERUM DURING DEVELOPMENT OF MULATTA,M .I. DURING FIRST YEAR OF LIFE

Extract The serum levels of free amino acids have been investigated during the first year of postnatal life in the rhesus monkey (M. mulatta). Samples of umbilical vein blood were obtained following normal full-term pregnancies. Infant monkeys were fed Similac®, a proprietary milk formulation with constant amino acid composition, at four-hour intervals throughout the first year of life. Blood samples were obtained at 2 weeks and at 1, 3, 6, 9 and 12 months of age, and the serum analyzed for all free amino acids. A wide range of values was evident for each amino acid at each age studied (table I). When all values obtained for each amino acid during the entire first year were analyzed, however, it was apparent that taurine, lysine, and 3-methyl-histidine were significantly elevated, and serine, tyrosine, and leucine were significantly reduced in the umbilical vein samples. By the end of the first month of life, values for all amino acids were within the normal range for adolescent and nonpregnant adult animals; further significant changes in amino acid levels did not occur during the remainder of the year of study. Speculation The nutritional correlates of growth and development in most laboratory animals are sufficiently different from those in the human to question their use in studies related to human nutrition. This study demonstrates that the patterns of change in the free amino acids of serum in the infant rhesus monkey are generally comparable to those observed in the human infant, and indicates that this species may be a suitable experimental counterpart for investigations of protein and amino acid metabolism which cannot be performed in children. © International Pediatrics Research Foundation, Inc. 1968. All Rights Reserved.