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Studies on the transfer machinery of sugar transfer in the placeental barrier.

胎盘屏障糖转运机制的研究。

基本信息

批准号：
08671869
负责人：
FUJIKURA Keiko
金额：
$ 1.22万
依托单位：
GUNMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

In order to elucidate the molecular mechanism of- sugar transfer in the placenta, we analyzed the localization of 'glucose transporter GLUT1, GLUT3, and gap junction proteins connexins in the rat placenta by immunohistochemical methods. Anti-rat GLUT3 antibody was raised using synthetic peptides corresponding to the isoform- specific stretch of GLUT3 molecules. GLUT1 was found in all, part of the placenta, whereas GLUT3 was restricted to the labyrinthine region, a site of materno-fetal transfer of sugars. Two layers of syncytiotrophoblasts (I and II from the maternal-blood side) constitute the barrier in the labyrinth, where both GLUT1 and GLUT3 were abundant. Immunogold electron microscopy revealed that GLUT1 was localized at the maternal-side plasma membrane of syncytiotrophoblast I and the fetal-side plasma membrane of, syncytiotrophoblast II.GLUT3 was localized at the at the maternal- side plasma membrane of syncytiotrophoblasts I and II.Syncytiotrophoblasts I and II were connected by numerous gap junctions made of connexin 26. These observations suggest that 1) both GLUT1 and GLUT3 serve in the entry of sugars into the cells of the placental barrier ; 2) gap junctions of connexin 26, hydrophilic channels connecting the cytoplasm of syncytiotrophoblasts I and II, serve as routes of sugar transfer in the barrier ; 3) GLUT1 serves as a transporter of sugars for the exit from the barrier. Recent connexin 26 knock-out experiment supports the above model. In addition, asymmetrical localization of GLUT3 in the placental barrier may serve for the polarized transfer of sugar across the placental barrier, possibly facilitates the stabilization of the fetal blood sugar level.

为了阐明胎盘中糖转移的分子机制，我们采用免疫组织化学方法分析了大鼠胎盘中葡萄糖转运蛋白GLUT1、GLUT3和间隙连接蛋白连接蛋白的定位。利用与GLUT3分子同种异构体特异性延伸相对应的合成肽，制备抗大鼠GLUT3抗体。GLUT1存在于胎盘的所有部分，而GLUT3则局限于迷宫区，这是一个母胎糖转移的地方。两层合胞滋养细胞（来自母血侧的I和II）构成了迷宫中的屏障，其中GLUT1和GLUT3都很丰富。免疫金电镜显示，GLUT1定位于合胞滋养细胞I母侧质膜和合胞滋养细胞II胎侧质膜。GLUT3定位于合胞滋养细胞I和II母侧质膜。合体滋养细胞I和II由连接蛋白26形成的大量间隙连接连接在一起。这些观察结果表明：1)GLUT1和GLUT3都参与糖进入胎盘屏障细胞；2)连接蛋白26的间隙连接，即连接合体滋养细胞I和II细胞质的亲水性通道，作为屏障中糖转移的途径；3) GLUT1作为糖的转运体从屏障中退出。最近的connexin 26敲除实验支持上述模型。此外，GLUT3在胎盘屏障中的不对称定位可能有助于糖在胎盘屏障中的极化转移，可能有助于胎儿血糖水平的稳定。