Amino acid concentrations in fetal and maternal plasma

Summary Fetal and maternal plasma samples, obtained at the time of cesarean section, were analyzed by column ion exchange chromatography for individual amino acids. The oncentrations of 9 individual and 3 paired amino acids, plus taurine and urea, are compared. Each amino acid with the exception of proline was found to exist in higher concentration in the fetal blood. This was found to be true when fetal and maternal blood samples were drawn simultaneously and also when maternal samples were compared to blood samples obtained from the newborn infants of other mothers. The data are presumed to be evidence favoring an active, mediated transport of the amino acids across the placental barrier. The relationship of these findings to the rate of fetal protein synthesis and to the endocrine control of the cellular uptake of free amino acids is discussed.