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Quarterly Journal of Experimental Physiology 74.5 pp 635-643
© The Physiological Society 1989
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UPTAKE OF AMINO ACIDS AND AMMONIA AT MID-GESTATION BY THE FETAL LAMB

Alan W. Bell 1, Jan M. Kennaugh 1, Frederick C. Battaglia 1, and Giacomo Meschia 1

1 Division of Perinatal Medicine, Departments of Pediatrics and Physiology, University of Colorado School of Medicine, Denver, CO 80262, USA

Fetal uptakes of amino acids and ammonia via the umbilical circulation were measured in single pregnant ewes at mid-gestation (range 66-81 days). There were significant net fluxes from placenta to fetus of ammonia and twelve amino acids (in decreasing order: glutamine, glycine, alanine, proline, lysine, arginine, threonine, valine, leucine, tyrosine, asparagine, isoleucine) and net fluxes from fetus to placenta of glutamate and serine. The estimated serine flux was 139 µmol day-1 (g fetal dry wt)-1. Comparison with late gestation data indicated a similar pattern of amino acid exchange. However, the relatively large placental uptake of fetal serine was a distinctive feature of mid-gestation. The net fetal uptake of amino acid nitrogen was 2·83 ± 0·66 µg N (µmol O2 uptake)-1, or 18 mg N day-1 (g dry wt)-1. This uptake was similar in magnitude to the combined fetal requirements for nitrogen accretion and urea synthesis and represented approximately 32 and 43% of fetal carbon and energy requirements, respectively.

Submitted on December 7, 1988
Accepted on April 6, 1989




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