Net amino acid flux across the fetal liver and placenta during spontaneousovine parturition

The uptake and/or release of amino acids across the feta I liver and the pl acenta were studied in 8 pregnant sheep during the 5 days preceding deliver y of the lamb. During spontaneous parturition, there was a significant decr ease in fetal hepatic glutamine uptake, in fetal hepatic glutamate release and in placental glutamate uptake. The fetal plasma concentrations of gluta mate, leucine, isoleucine, valine, phenylalanine, serine and tyrosine also decreased significantly in the 5 days preceding delivery. There was no sign ificant net output of glucose from the fetal liver nor any change in net la ctate uptake by the liver. During this same time period there was a signifi cant increase in the fetal plasma cortisol concentration and a decrease in progesterone output by the pregnant uterus. The results are compared to the previously reported amino acid changes during dexamethasone-induced partur ition. Copyright (C) 2001 S. Karger AG, Basel.