Production and utilization of amino acids by ovine placenta in
vivo.
Chung, Misoo, Cecilia Teng, Michelle Timmerman, Giacomo Meschia, and
Frederick C. Battaglia.
Division of Perinatal Medicine, Departments of Physiology,
Obstetrics-Gynecology and Pediatrics, University of Colorado School
of Medicine, Denver, CO 80262
APStracts 4:0212E, 1997.
Uterine and umbilical uptakes of plasma amino acids were measured
simultaneously in eighteen singleton pregnant ewes at 130 +/- 1 days
gestation, for the purpose of establishing which amino acids are
produced or utilized by the uteroplacenta under normal physiologic
conditions, and at what rates. The branched chain amino acids (BCAA)
had uterine uptakes significantly greater than umbilical uptakes. Net
uteroplacental BCAA utilization was 8.0 +/- 2.5 [mu]molxKgfetus
-1xmin-1 (p < 0.005), and represented 42% of the total BCAA
utilization by fetus plus uteroplacenta. There was placental uptake
of fetal glutamate (4.2 +/- 0.3 [mu]molxKgfetus-1xmin-1, p < 0.001)
and no uterine uptake of maternal glutamate. Umbilical uptake of
glutamine was approximately 61% greater than uterine uptake, thus
demonstrating net uteroplacental glutamine production of 2.2 _+/-_
0.9 _[mu]_mol_x_Kgfetus-1_x_min-1 (p < 0.021). In conjunction with
other evidence, these data indicate rapid placental metabolism of
glutamate, which is supplied in part by the fetus and in part
produced locally via BCAA transamination. Most of the glutamate is
oxidized and some is used to synthesize glutamine which is delivered
to the fetus. There was net uteroplacental utilization of maternal
serine and umbilical uptake of glycine produced by the placenta.
Maternal serine utilization and glycine umbilical uptake were
virtually equal (3.14 _+/-_ 0.50 vs. 3.10 _+/-_ 0.46
_[mu]_mol_x_Kgfetus-1_x_min-1). This evidence supports the conclusion
that the ovine placenta converts large quantities of maternal serine
into fetal glycine.
Received 27 May 1997; accepted in final form 4 September 1997.
APS Manuscript Number E242-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 7 October 1997