THE GLUT3 GLUCOSE-TRANSPORTER ISOFORM IS DIFFERENTIALLY EXPRESSED WITHIN HUMAN PLACENTAL CELL-TYPES

The cellular localization of GLUTS messenger ribonucleic acid (mRNA) a nd protein was examined in human term placenta using a combination of methodologies. In situ hybridization indicated that GLUTS mRNA was pre sent in the trophoblast cell layer and in vascular endothelium with a heterogeneous distribution pattern. GLUTS protein migrating at an appa rent molecular mass of 49 kDa was detected by immunoblotting in membra nes from whole placenta and endothelial cells derived from intraplacen tal microvessels, but not in isolated trophoblast cells. This cell-spe cific pattern of expression was confirmed by immunocytochemical studie s showing a prominent localization of GLUTS protein in vascular endoth elium. These findings indicate a differential distribution of GLUT3 mR NA and protein in the human placenta. Based on its cell-specific distr ibution at the fetal interface, GLUTS protein could be of cardinal imp ortance in the transport of glucose from the placenta to the fetal cir culation.