D‐amino acid levels in human physiological fluids

Plasma, urine, cerebrospinal fluid (CSF), and amniotic fluid were examined to determine whether free D-amino acids were present and if so at what levels. It was found that D-amino acids exist in all physiological fluids tested, but that their level varied considerably. The lowest levels of D-amino acids were usually found in amniotic fluid or CSF (almost always 90%). Correspondingly high levels of D-pipecolic acid were not found in plasma. Some of the trends found in this work seemed to be analogous to those found in a recent rodent study.