Department of Pediatrics, Division of Perinatal Medicine, University of Colorado, Aurora, Colorado, USA.
Pediatr Res. 2013 May;73(5):602-11. doi: 10.1038/pr.2013.30. Epub 2013 Feb 13.
This study examines the relationship between placental amino acid (AA) transport and fetal AA demand in an ovine fetal growth restriction (FGR) model in which placental underdevelopment induces fetal hypoxemia and hypoglycemia.
Umbilical uptakes of AA, oxygen, glucose, and lactate were measured near term in eight experimental ewes (FGR group) and in eight controls (C group).
The FGR group demonstrated significantly reduced umbilical uptakes of oxygen, glucose, lactate, and 11 AAs per kg fetus. The combined uptake of glucose, lactate, and AAs, expressed as nutrient/oxygen quotients, was reduced almost to 1.00 (FGR: 1.05 vs. C: 1.32, P ≤ 0.02). In contrast to a decrease in umbilical glucose concentration, all but one of the AAs that were transported from placenta to fetus demonstrated normal or elevated fetal concentrations, and five of the essential AAs were transported against a significantly higher feto/maternal (F/M) concentration ratio. This ratio peaked at the lowest fetal oxygen levels.
We conclude that, in the hypoxic FGR fetus, the reduction in AA uptake is not due to a disproportionally small placental AA transport capacity. It is the consequence of decreased fetal oxidative metabolism and growth rate, which together reduce fetal AA demand.
本研究在羊胎儿生长受限（FGR）模型中研究了胎盘氨基酸（AA）转运与胎儿 AA 需求之间的关系，该模型中胎盘发育不良导致胎儿低氧血症和低血糖。
在 8 只实验母羊（FGR 组）和 8 只对照母羊（C 组）临近分娩时，测量脐带上 AA、氧、葡萄糖和乳酸的摄取情况。
FGR 组胎儿脐带上的氧、葡萄糖、乳酸和 11 种 AA 的摄取量明显减少。以营养/氧比值表示的葡萄糖、乳酸和 AA 的综合摄取量几乎降低到 1.00（FGR：1.05 比 C：1.32，P≤0.02）。与脐葡萄糖浓度降低相反，从胎盘转运到胎儿的除一种 AA 外，所有 AA 的胎儿浓度均正常或升高，5 种必需 AA 以明显更高的胎/母（F/M）浓度比转运。该比值在最低胎儿氧水平时达到峰值。
我们的结论是，在缺氧性 FGR 胎儿中，AA 摄取量的减少不是由于胎盘 AA 转运能力不成比例地小。这是胎儿氧化代谢和生长速度下降的结果，共同降低了胎儿对 AA 的需求。
