The GLUT3 glucose transporter isoform is differentially expressed within human placental cell types

The cellular localization of GLUTS messenger ribonucleic acid (mRNA) and protein was examined in human term placenta using a combination of methodologies. In situ hybridization indicated that GLUTS mRNA was present in the trophoblast cell layer and in vascular endothelium with a heterogeneous distribution pattern. GLUTS protein migrating at an apparent molecular mass of 49 kDa was detected by immunoblotting in membranes from whole placenta and endothelial cells derived from intraplacental microvessels, but not in isolated trophoblast cells. This cell-specific pattern of expression was confirmed by immunocytochemical studies showing a prominent localization of GLUTS protein in vascular endothelium. These findings indicate a differential distribution of GLUT3 mRNA and protein in the human placenta. Based on its cell-specific distribution at the fetal interface, GLUTS protein could be of cardinal importance in the transport of glucose from the placenta to the fetal circulation.