The Free Amino Acids of Brain and Liver during Fetal Life of Macaca mulatta ∗

The relative concentrations of all free amino acids which can be part of protein molecules of animal tissue probably influence the rate of protein synthesis at the cellular level. The other ninhydrin positive compounds in the cell detected during free amino acid analysis should indicate the metabolic activity of these low-molecular weight compounds.

In this report the free amino acid levels in the brain and the liver of fetal monkeys at different stages of gestation and shortly after birth are given. These data are part of a study of fetal development in a subhuman primate, whose placenta is structurally comparable to the human placenta. Other parts of this developmental study referring to free amino acids in the serum during pregnancy and fetal life of the M. mulatta have been reported by Kerr (1).

Although several studies can be found in the literature on free brain amino acids in young animals, fragmentary data on only a small number of fetal brains are available, and then mostly as part of another study. Carver et al. (2) compared free amino acids in fetal rat brain at 19 and 21 days gestation. Dravid et al. (3) determined some free amino acids in dog brain during development, but only a part of this study was concerned with the analysis of a whole fetal brain. No investigation into the free amino acid content of fetal liver of any animal or human has come to our attention.

Materials and Methods. The design of the fetal study and information on fetal specimens of known gestational age obtained by cesarean section have been described in detail by Kerr (1). Surgery was performed under local anesthesia 8–12 hr after the last feeding.