Free amino acids in the blood of fetal and maternal Weddell seals.

Abstract

The content of free amino acids in whole blood was measured in near-term gravid female Weddell seals (Leptonychotes weddelli) and compared with fetal amino acid profiles during rest and during experimental diving. With the exception of taurine and glutathione, Ninhydrin-reactive components of acid extracts of blood occurred in higher concentrations on the fetal side of the placenta than on the maternal side. Compared with humans the Weddell seal displayed higher ratios of fetal arterial to maternal arterial levels for aspartate, glycine, alanine, valine, tyrosine, phenylalanine, and total branched-chain amino acids. In the resting state the total free amino acid concentration in maternal blood was only about 70% as large as the total amino acid concentration in fetal blood, compared with a value of over 80% for humans. Only modest changes in the concentrations of specific amino acids occurred during simulated awake diving, but the overall maternal pools of glycine, glutamate, and glutamine were augmented, creating favorable conditions for uptake by the fetus.