The mechanisms and regulation of placental nutrient transport.

向胎儿提供营养是胎盘的主要功能之一。胎儿的发育依赖于胎盘的营养供应，营养供应不足会增加胎儿和围产期疾病的风险。我们先前的研究表明，为胎儿提供叶酸的转运蛋白的表达水平随着妊娠的进展而变化。系统N转运蛋白SNAT 3在妊娠早期即有表达，随着妊娠的进行其表达水平逐渐降低。SNAT 3在人原代细胞滋养层细胞中也有表达，随着细胞向合体滋养层细胞的分化，其表达水平降低，由于这种调节与谷氨酰胺合成酶的表达密切相关，因此SNAT 3可能在妊娠早期提供谷氨酰胺合成酶功能所对应的谷氨酰胺中起关键作用。这是首次报道SNAT 3在妊娠早期胎盘中的表达。

Supply of nutrients to the fetus is one of main functions of the placenta. Fetal development is dependent on placental nutrient supply, and insufficient nutrient supply increases the risk of fetal and perinatal diseases. We previously showed that the expression levels of transporters that provide folate to the fetus change with progress of gestation. The expression of SNAT3, the system N transporter, was detected in the early period of pregnancy and its expression level decreased as gestation progressed. SNAT3 was also found to be expressed in isolated human primary cytotrophoblast cells and its expression level was decreased by their differentiation into syncytiotrophoblast cells.Since this regulation is closely related to glutamine synthetase expression, SNAT3 may play a key role in providing glutamine corresponding to glutamine synthetase function in the early period of gestation. This is the first report on the expression of SNAT3 in the placenta in the early stage of pregnancy.