title: Kinetics of amino acid metabolism in the ovine fetus in utero.
abstract: The recycling of amino acids in chronically catheterized ovine fetuses was determined using a single intravenous injection of a mixture of fifteen (U-14C) amino acids. The specific activity--time data were fitted to a three exponential curve which best represented the disappearance of the tracer from the fetal blood plasma. Based on the rates of total entry and irreversible disposal of amino acid carbon, it was determined that 85% of the free amino acid pool was recycled. In addition, 23.6% of the administered label was recovered in fetal blood 14CO2. No radioactivity was detectable in the maternal plasma after the injection of tracer into the fetus. The mean total residence time of the label in the fetuses studied was 7.22 +/- 0.89 minutes and corresponded to 6.46 +/- 0.93 metabolic cycles. The high rate of recycling of amino acids in the plasma pool is a reflection of the rapid turnover of proteins in the actively growing fetus.
mesh_terms: D000596:Amino Acids / Q000097:blood / Q000378:metabolism*; D000818:Animals; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005333:Fetus / Q000378:metabolism*; D006207:Half-Life; D007700:Kinetics; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D012756:Sheep / Q000196:embryology*
chemical_list: D000596:Amino Acids