D-AMINO-ACID LEVELS IN HUMAN PHYSIOLOGICAL FLUIDS

Plasma, urine, cerebrospinal fluid (CSF), and amniotic fluid were exam ined 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 physiologic al fluids tested, but that their level varied, considerably. The lowes t levels of D-amino acids were usually found in amniotic fluid or CSF (almost always <1% of the corresponding L-amino acid). The highest lev els were found in urine (usually tenth percent to low percent levels). Pipecolic acid seemed to be different from the other amino acids test ed in that it was excreted primarily as the D-enantiomer (often >90%). Correspondingly high levels of D-pipecolic acid were not found in pla sma. Some of the trends found in this work seemed to be analogous to t hose found in a recent rodent study. (C) 1993 Wiley-Liss, Inc.