Marconi A M, Battaglia F C, Meschia G, Sparks J W
Department of Obstetrics-Gynecology, University of Colorado School of Medicine, Denver 80262.
Am J Physiol. 1989 Dec;257(6 Pt 1):E909-15. doi: 10.1152/ajpendo.1989.257.6.E909.
Amino acid and ammonia concentrations as well as oxygen content were measured in either the right or left hepatic vein, the umbilical vein, and the umbilical artery in 13 fetal lambs in late gestation. There was an uptake of all of the essential and most of the nonessential amino acids by both lobes of the fetal liver. The umbilical venous-hepatic venous amino acid concentration differences were similar in the two hepatic lobes. While glutamine and glycine were taken up by both hepatic lobes, their metabolically related amino acids, glutamate and serine, were released by the fetal liver into the systemic circulation. There was a reciprocal net placental uptake from the umbilical circulation of glutamate and serine and a net fetal of glutamine and glycine, suggestive of interorgan cycling of these amino acids between the placenta and fetal liver. Total fetal umbilical nitrogen uptake was 0.91 g N.kg-1.day-1. The umbilical venous-hepatic venous differences of ammonia were positive and not significantly different in the two lobes. There was a significant umbilical uptake of ammonia (12.8 +/- 1.8 microM; 0.0078 microM NH3/microM O2). However, 0 the ratios of NH3 to O2 were much higher in each lobe (right, 0.060; left, 0.079; each P less than 0.01) than in the umbilical circulation.
在13只妊娠晚期的胎羊中，测量了其右或左肝静脉、脐静脉和脐动脉中的氨基酸、氨浓度以及氧含量。胎儿肝脏的两叶均摄取了所有必需氨基酸和大部分非必需氨基酸。两叶肝脏中脐静脉 - 肝静脉的氨基酸浓度差异相似。虽然谷氨酰胺和甘氨酸被两叶肝脏摄取，但其代谢相关氨基酸谷氨酸和丝氨酸却由胎儿肝脏释放进入体循环。脐循环中谷氨酸和丝氨酸有胎盘净摄取，谷氨酰胺和甘氨酸有胎儿净摄取，提示这些氨基酸在胎盘和胎儿肝脏之间存在器官间循环。胎儿脐部总的氮摄取量为0.91 g N·kg⁻¹·d⁻¹。两叶肝脏中氨的脐静脉 - 肝静脉差异为正值且无显著差异。脐部有显著的氨摄取（12.8±1.8 μmol；0.0078 μmol NH₃/μmol O₂）。然而，每叶肝脏中NH₃与O₂的比值（右叶为0.060；左叶为0.079；P均＜0.01）远高于脐循环中的比值。
