Takata K, Hirano H
Laboratory of Molecular and Cellular Morphology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.
Microsc Res Tech. 1997;38(1-2):145-52. doi: 10.1002/(SICI)1097-0029(19970701/15)38:1/2<145::AID-JEMT15>3.0.CO;2-P.
Glucose is one of the most important substances transferred from the maternal blood to the fetal circulation in the placenta, and its transport across the cellular membranes is mediated by glucose transporters. Facilitated-diffusion glucose transporter GLUT1 is abundant in the placental barrier, as is the case in other blood-tissue barriers, where GLUT1 is present at the critical plasma membranes of the barrier cells. In the human placenta, the microvillous apical and the basal plasma membranes of the syncytiotrophoblast are rich in GLUT1, which molecule seems to be responsible for the transcellular transport of glucose across the placental barrier. In the rat placental labyrinth, two layers of syncytiotrophoblasts (termed syncytiotrophoblasts I and II from the maternal side) serve as a barrier. GLUT1 is abundant at the plasma membrane of syncytiotrophoblast I facing the maternal side, and the plasma membrane of syncytiotrophoblast II facing the fetal side. Numerous gap junctions, made of connexin 26, connect syncytiotrophoblasts I and II, comprising a channel for the transfer of glucose between them. GLUT1 in combination with the gap junction, therefore, seems to serve as the structural basis for the transport of glucose across the rat placental barrier.
葡萄糖是经胎盘从母体血液转运至胎儿循环的最重要物质之一，其跨细胞膜转运由葡萄糖转运蛋白介导。易化扩散型葡萄糖转运蛋白1（GLUT1）在胎盘屏障中含量丰富，其他血组织屏障也是如此，GLUT1存在于屏障细胞的关键质膜上。在人胎盘中，合体滋养层细胞的微绒毛顶端质膜和基底质膜富含GLUT1，该分子似乎负责葡萄糖跨胎盘屏障的跨细胞转运。在大鼠胎盘迷路中，两层合体滋养层细胞（从母体侧起称为合体滋养层细胞I和II）构成一道屏障。GLUT1在面向母体侧的合体滋养层细胞I的质膜以及面向胎儿侧的合体滋养层细胞II的质膜上含量丰富。由连接蛋白26构成的众多缝隙连接将合体滋养层细胞I和II连接起来，形成一个它们之间葡萄糖转运的通道。因此，GLUT1与缝隙连接相结合，似乎构成了葡萄糖跨大鼠胎盘屏障转运的结构基础。
