LOCALIZATION OF THE HIGH-AFFINITY FACILITATIVE GLUCOSE-TRANSPORTER PROTEIN GLUT-1 IN THE PLACENTA OF HUMAN, MARMOSET MONKEY (CALLITHRIX-JACCHUS) AND RAT AT DIFFERENT DEVELOPMENTAL STAGES

In the present study, the facilitative D-glucose transporter protein GLUT 1 was localised by immunohistochemisty in the placenta of human, marmoset (Callithrix jacchus) and rat at different developmental stages. A polyclonal antiserum against a 13-amino-acid peptide of the GLUT 1 carboxy terminus was used. It identified a protein of around 50 kDa molecular weight in immunoblotting of the placental tissues. GLUT 1 was located in the syncytiotrophoblast, in cytotrophoblast cells and in fetal endothelium. Similar staining patterns, except in human extravillous cytotrophoblast cells, were observed at all differentiation stages, despite differences in the internal placental architecture of the species. In the marmoset placenta, GLUT 1 was undetectable in endothelial cells of maternal vessels. In rat placentae, trophoblastic giant cells, epithelial cells of both visceral and parietal yolk sac, yolk sac vessels and the stratum spongiosum were stained. Reichert's membrane did not immunoreact. Preadsorption of the antiserum with a 13-amino-acid peptide resulted in the loss of immunoreactivity. The results suggest that GLUT 1 is a prominent isoform of glucose transporters in mammalian placentae. It is generally abundant in placental cell populations bordering on the maternal and fetal circulations and may therefore facilitate an effective glucose supply to the fetus and placenta.