Localization of human placental glucose transporter 1 during pregnancy. An immunohistochemical study

To elucidate the potential roles of glucose transporter 1 (GLUT1) in human placenta during pregnancy, we examined the localization of GLUT1 in human placenta at various stages by immunohistochemistry with an anti-GLUT1 antibody by use of both light and electron microscopy. Specific staining for GLUT1 was localized on the apical brush border and along the basal plasma membrane of the syncytiotrophoblasts. The staining at the apical side was more intense than that at the basal side during the early stages of gestation. In later gestational stages, however, the staining pattern at the apical side became blurred and the staining intensity at the basal side increased. The cytotrophoblasts, seen embedded in the basal part of the syncytiotrophoblasts, seemed to show immunoreactivity for GLUT1 along the plasma membranes at the light-microscopic level. However, immuno-electron microscopic analysis with either pre- or post-embedding methods revealed that specific staining for GLUT1 was hardly observed on the cytotrophoblasts, but the cytotrophoblasts were often surrounded by immunoreactive processes of syncytiotrophoblasts. The blood capillaries and erythrocytes in the stroma of placental villi were always immunoreactive for GLUT1 throughout pregnancy. These findings suggest that GLUT1 may play a vital role in human pregnancy.