Wilkening R B, Boyle D W, Teng C, Meschia G, Battaglia F C
Department of Pediatrics, University of Colorado School of Medicine, Denver 80262.
Am J Physiol. 1994 Jan;266(1 Pt 1):E72-8. doi: 10.1152/ajpendo.1994.266.1.E72.
As part of an effort to establish the contribution of different fetal organs to fetal amino acid metabolism, we measured in nine sheep fetuses the uptake of 27 amino acids by the hindlimb under normal conditions and conditions by euglycemic hyperinsulinemia. The fetal hindlimb is representative of nonvisceral tissues, which in the mature fetus account for approximately 70% of fetal weight and 30% of fetal O2 consumption. In the normal condition, there was a significant uptake of 21 amino acids for a net total nitrogen uptake of 132 +/- 21 mg N.day-1 x 100 g-1. The amino acids taken up by the fetal limb included alanine and glutamine. In addition, the fetal limb had significant glutamate and serine uptakes. Because glutamate flows from fetus to placenta and there is no fetal uptake of maternal serine, this indicates production and interorgan transport of these amino acids within the fetus. Insulin infusion significantly decreased the arterial concentration of every amino acid with the exception of cystathionine and significantly increased limb blood flow and glucose uptake. It significantly increased the limb uptake of alanine, asparagine, glycine, isoleucine, methionine, and tyrosine, decreased the uptake of aspartate, and produced no significant change in the net total nitrogen uptake, which remained similar to control (137 +/- 16 mg N.day-1 x 100 g-1).
为确定不同胎儿器官对胎儿氨基酸代谢的贡献，我们对9只绵羊胎儿在正常条件及正常血糖高胰岛素血症条件下后肢对27种氨基酸的摄取情况进行了测量。胎儿后肢代表非内脏组织，在成熟胎儿中，非内脏组织约占胎儿体重的70%及胎儿耗氧量的30%。在正常情况下，有21种氨基酸有显著摄取，净总氮摄取量为132±21mg N·天⁻¹×100g⁻¹。胎儿肢体摄取的氨基酸包括丙氨酸和谷氨酰胺。此外，胎儿肢体对谷氨酸和丝氨酸有显著摄取。由于谷氨酸从胎儿流向胎盘，且胎儿不摄取母体丝氨酸，这表明这些氨基酸在胎儿体内的产生和器官间转运。输注胰岛素显著降低了除胱硫醚外每种氨基酸的动脉浓度，并显著增加了肢体血流量和葡萄糖摄取。它显著增加了肢体对丙氨酸、天冬酰胺、甘氨酸、异亮氨酸、蛋氨酸和酪氨酸的摄取，降低了天冬氨酸的摄取，且净总氮摄取没有显著变化，仍与对照组相似（137±16mg N·天⁻¹×100g⁻¹）。
