Effect of low-protein diet-induced intrauterine growth retardation on rat placental amino acid transport
Effect of low-protein diet-induced intrauterine growth retardation on rat placental amino acid transport
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DOI：
10.1152/ajpcell.1996.271.1.c295
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发表时间：
1996-07-01
影响因子：
5.5
通讯作者：
Novak, DA
中科院分区：
文献类型：
--
作者：
Malandro, MS;Beveridge, MJ;Novak, DA
考虑到胎盘在向胎儿输送营养方面的中心作用，有人可能会提出母体营养对这种营养输送具有调节作用。我们研究了低蛋白、足够热量饮食对大鼠胎盘特定氨基酸转运过程的影响。与饲喂对照（20%酪蛋白）饲料的母鼠配对相比，饲喂低蛋白（5%酪蛋白）等热量饲料的母鼠的母体重量、胎仔重量和胎盘重量均显著降低。尽管低蛋白动物的母体血清氨基酸水平得以维持，但母胎血清氨基酸比率显著降低，表明向胎儿的营养转移减少。从胎盘滋养层细胞中分离出顶膜和基膜囊泡，并分别用于检查面向母体和面向胎儿的膜的氨基酸转运能力。Na+-依赖性中性氨基酸转运介导的系统A在两种膜制剂减少，而运输介导的系统ASC不受影响。Na+依赖性的阴离子氨基酸吸收系统X（AG）（-）（EAAC 1）减少基膜，而Na+的非依赖性成分之间的低蛋白和对照饲料喂养的母鼠是相似的。阳离子氨基酸的吸收也减少了两个膜表面。EAAC 1和CAT 1（系统y（+））的稳态mRNA含量降低表明转运蛋白合成减少是转运活性降低的原因。总之，这些数据支持了母体蛋白质营养不良通过下调特定氨基酸转运蛋白影响胎儿营养输送的假设。
Given the central role of the placenta in nutrient transport to the fetus, one might propose that maternal nutrition would have a regulatory effect on this nutrient delivery. We have examined the effect of a low-protein adequate-calorie diet on specific amino acid transport processes by the rat placenta. Maternal weight, fetal weight, and placental weight were all significantly reduced in dams fed a low-protein (5% casein), isocaloric diet when compared with dams pair-fed a control (20% casein) diet. Even though maternal serum amino acid levels were maintained in the low-protein animals, fetomaternal serum amino acid ratios were significantly reduced, suggesting a reduction in nutrient transfer to the fetus. Apical and basal membrane vesicles were isolated from the placental trophoblast and were used to examine the amino acid transport capacity of both maternal-facing and fetal-facing membranes, respectively. Na+-dependent neutral amino acid transport mediated by system A was decreased in both membrane preparations, while transport mediated by system ASC was unaffected. The Na+-dependent anionic amino acid uptake by system X(AG)(-) (EAAC1) was reduced on the basal membrane, while the Na+-independent component was similar between the low-protein and control diet-fed dams. Cationic amino acid uptake was also reduced on both membrane surfaces. A decreased steady-state mRNA content for EAAC1 and CAT1 (system y(+)) suggests that reduced synthesis of the transporter proteins is responsible for the decrease in transport activity. Taken together, these data support the hypothesis that maternal protein malnutrition affects nutrient delivery to the fetus by downregulation of specific amino acid transport proteins.