GLUCOSE-TRANSPORTER GLUT3 IN THE RAT PLACENTAL BARRIER - A POSSIBLE MACHINERY FOR THE TRANSPLACENTAL TRANSFER OF GLUCOSE

Glucose transfer across the placental barrier is crucial for fetal dev elopment. To investigate the role of glucose transporter isoforms in t he transplacental transfer of glucose, we investigated the localizatio n of glucose transporters GLUT1 and GLUT3 immunohistochemically in the rat placenta. In the labyrinth, the site of maternofetal exchange of substances, both GLUT1 and GLUT3 were present, whereas only GLUT1 was detected in the junctional region. In the labyrinthine wall, which lie s between maternal and fetal circulations, GLUT3 exhibited polarized l ocalization; i.e. it was present at the plasma membranes of the matern al blood side in the syncytiotrophoblast layers. GLUT1 was concentrate d at plasma membranes of the maternal and fetal blood sides of syncyti otrophoblast layers. The asymmetric distribution of GLUT3 across the p lacental barrier may suggest asymmetric transfer of glucose, which wou ld be beneficial to provide a stable milieu for fetal development.