Immunohistochemical localization of glucose transporters and insulin receptors in human fetal membranes at term

Abstract

The localization has been investigated of the isoforms GLUT1, GLUT3 and GLUT4 of glucose transporter proteins as well as of insulin receptors. Fetal membranes (n = 10) were examined by immunohistochemical methods at the light and electron microscopic levels using mono- and polyclonal antibodies. In all amnion epithelial cells, GLUT1 and GLUT3 antibodies were bound to the apical membrane. Very rarely the GLUT1 antibody also immunostained the basolateral membrane and reacted weakly with the endomembrane system and membranes of the lateral cell protrusions. Fibroblasts reacted with the antibodies against GLUT1, GLUT4 and insulin receptor, whereas they were labelled only in one case with GLUT3 antibody. Cytotrophoblast cells were only stained with antibodies against GLUT1 and GLUT3. Antibodies against GLUT4 only reacted with fibroblasts in the membranes. On amnion epithelial cells, weak immunoreactivity with insulin receptor antibodies was detected only at the electron microscopic level. The data indicate: (1) GLUT1 is located on all cells of the amnion, whereas GLUT3 is present in detectable amounts only on amnion epithelial cells and cytotrophoblast; (2) GLUT1 and GLUT3 on amnion epithelial cells are predominantly located on the apical surface; (3) GLUT4 and insulin receptors are not regularly expressed. We suggest that amnion epithelial cells cover their basal glucose requirements from the amniotic fluid and not from the maternal circulation.

The Effects of Glucocorticoids on Fetal and Placental Development

“…GLUT3 mRNA is distributed throughout the cells of villous tissue; GLUT3 protein appears to be expressed only in the vascular endothelium and, is not expressed in the syncytiotrophoblast layer of the placenta. A strong GLUT4 signal was observed in intravillous stromal cells, appearing to co-localize with insulin receptors [136], a discovery which complements the observation of GLUT4 in fibroblasts from amnion and chorion [137].…”

Hypoxic Regulation of Glucose Transport, Anaerobic Metabolism and Angiogenesis in Cancer: Novel Pathways and Targets for Anticancer Therapeutics

“…GLUT1 is not detectable in aortic smooth muscle ( a ) but is moderately expressed in cardiac muscle ( b ) and skeletal muscle ( c ). GLUT1 is present in articular chondrocytes ( d ), amniotic membranes ( e ) [216] , placenta ( f ) [217] and in microvessels [218,219] in various regions of the central nervous system including cerebral cortex ( g ), choroid plexus ( h ) and hippocampus ( i ). Expression in the choroid plexus was predominantly basolateral [220] .…”

Overexpression of GLUT3 placental glucose transporter in diabetic rats.

“…At least five different facilitative glucose transporters encoded by separate genes (GLUTI -5) have been characterized in mammalian tissues (reviewed in reference 3,4). Among these transporters, GLUTI and GLUT3 proteins are predominantly expressed in human and rat placenta (5)(6)(7)(8). The mRNAs of these two major placental glucose transporter isoforms have been recently localized in the rat by in situ hybridization.…”