THE CLASSIC studies of Levine, Gordon, and Marples1,2 demonstrated a defect in aromatic amino-acid metabolism of premature infants receiving a high protein, low ascorbic acid diet. Application of screening studies for detection of phenylketonuria in newborn infants led to the observation of elevated levels of blood phenylalanine, particularly in premature infants. The phenylalanine elevation was associated with high blood levels of tyrosine. This metabolic peculiarity of prematures assumes practical import, for (a) the abnormal blood values may be confused with the blood findings of phenylketonuria and (b) this aberration of amino-acid metabolism may contribute directly or indirectly to the poor intellectual development of the prematurely born child. The present studies were undertaken to permit serial measurement of phenylalanine and tyrosine levels in blood from premature infants and to clarify the role of ascorbic acid in aromatic amino-acid metabolism.
Material and Methods
Subjects.—All infants born at the Cincinnati General