Free amino acid concentrations in normal and abnormal third trimester placental villi

Homogenates of placental villi were obtained from normotensive pregnancies and from pregnancies complicated by pre-eclampsia and growth retardation. The homogenates were analysed for free amino acid concentrations using high performance liquid chromatography (HPLC). The study shows that there are significantly higher concentrations of two essential amino acids, L-arginine and phenylalanine (P < 0.05), in the growth-retarded group compared to the term normotensive and pre-eclamptic groups. There are significantly higher concentrations of the non-essential amino acids: glutamic acid in the growth retarded group compared to the normotensive group, and of tyrosine in the growth-retarded group compared to the pre-eclamptic group. However, there is no increase in the glycine/valine ratio, a characteristic marker for kwashiorkor or a reduction in total protein concentration in the pre-eclamptic or growth-retarded groups. These findings suggest that there may be abnormalities in placental metabolism, amino acid transfer across the basal membrane into the fetal circulation, and also fetoplacental perfusion in pregnancies complicated by pre-eclampsia and growth retardation.