Free amino acids of normal and abnormal human placenta

The free amino acid content of human placenta has not previously been reported, although such levels are known for many normal and malignant tissues. Free amino acids in the placenta increase during pregnancy although they are already quite high by 20 weeks. Compared to studies of uterus and endometrium, placental aspartic acid is high and glutamic acid is normal, while asparagineglutamine is uniformly low, suggesting a deficiency of asparagine and glutamine synthetase. In hydatidiform mole, aspartic and glutamic acid levels are low while asparagine and glutamine levels are comparable to those of normal placenta, suggesting that transamination is not a major metabolic activity of trophoblast. Placental arginine is high compared to levels in normal uterus. All other essential amino acids show little variation. Free amino acid levels are low in infarcted placenta and high in toxemic placenta. All tissue samples exhibited low levels of valine and proline, suggesting they are active, rather than degenerating.