Immunolocalisation of nucleoside transporters in human placental trophoblast and endothelial cells: evidence for multiple transporter isoforms

Pflugers Arch. 1995 Jan;429(3):394-9. doi: 10.1007/BF00374155.


Polyclonal antibodies raised against the human erythrocyte nucleoside transporter were used to investigate the distribution of the nucleoside transporters in the placenta. Immunoblots of brush-border membranes isolated from the human syncytiotrophoblast revealed a cross-reactive species that co-migrated with the erythrocyte nucleoside transporter as a broad band of apparent M(r) 55,000. In contrast, no labelling was detected in basal membranes containing a similar number of equilibrative nucleoside transporters as assessed by nitrobenzylthioinosine (NBMPR)-binding. The absence of cross-reactive epitopes in basal membranes and their presence in brush-border membranes was confirmed by confocal immunofluorescence microscopy. These results suggest that at least two isoforms of the NBMPR-sensitive nucleoside transporter are present in the human placenta. The lumenal surfaces of fetal capillaries, small placental vessels and umbilical vein were also strongly labelled by the antibody, a finding that suggests that the high fetal-placental adenosine uptake previously reported is due to endothelial transporters.

MeSH terms

  • Affinity Labels
  • Carrier Proteins / metabolism*
  • Cell Membrane / metabolism
  • Endothelium / cytology
  • Endothelium / metabolism
  • Female
  • Humans
  • Immunoblotting
  • Immunohistochemistry
  • Isomerism
  • Membrane Proteins / metabolism*
  • Microscopy, Confocal
  • Microvilli / metabolism
  • Nucleoside Transport Proteins
  • Placenta / cytology
  • Placenta / metabolism*
  • Pregnancy
  • Thioinosine / analogs & derivatives
  • Thioinosine / metabolism
  • Trophoblasts / metabolism*
  • Umbilical Cord / cytology
  • Umbilical Cord / metabolism


  • Affinity Labels
  • Carrier Proteins
  • Membrane Proteins
  • Nucleoside Transport Proteins
  • Thioinosine
  • 4-nitrobenzylthioinosine