PEDIATRICS Vol. 45 No. 5 May 1970, pp. 782-791
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CIRCADIAN PERIODICITY OF BLOOD AMINO ACIDS IN THE NEONATE

Ralph D. Feigin M.D.1 and Morey W. Haymond M.D.1

1 Division of Infectious Diseases, Department of Pediatrics, Washington University School of Medicine, St. Louis Children's Hospital, St. Louis, Missouri

Blood amino acids were obtained every 4 hours for 24 hours from 46 full-term infants who were between 1 hour and 120 hours of age when first sampled. Blood was also obtained at 0400 and 1200 hours on the same day from 10 additional infants, aged 48 to 72 hours at the time of study, for more detailed analysis of individual blood amino acids. Periodicity of total blood amino acids was demonstrated as early as the first day of life in some infants. This blood amino acid rhythmicity was similar but not identical to that previously observed in adults and older children. Concentrations of blood amino acids were minimal at 0400 hours and peaked between 1200 and 2000 hours. Periodicity of individual blood amino acids was similar to that for total blood amino acids but much less consistent. The presence of periodicity for plasma tyrosine was demonstrable even in two patients with neonatal tyrosinemia.

Since plasma amino acids vary normally as a function of time, "normal values" must be standardized for time of day.

Submitted on October 17, 1969
Accepted on December 2, 1969