Immunolocalisation of nucleoside transporters in human placental trophoblast and endothelial cells: evidence for multiple transporter isoforms.
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.
Barros
L F
LF
Departmento of Fisiología y Biofísica, Universidad de Chile, Santiago.
Yudilevich
D L
DL
Jarvis
S M
SM
Beaumont
N
N
Young
J D
JD
Baldwin
S A
SA
D000345:Affinity Labels; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004727:Endothelium / Q000166:cytology / Q000378:metabolism; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007536:Isomerism; D008565:Membrane Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D008871:Microvilli / Q000378:metabolism; D033703:Nucleoside Transport Proteins; D010920:Placenta / Q000166:cytology / Q000378:metabolism*; D011247:Pregnancy; D013868:Thioinosine / Q000031:analogs & derivatives / Q000378:metabolism; D014327:Trophoblasts / Q000378:metabolism*; D014470:Umbilical Cord / Q000166:cytology / Q000378:metabolism
D000345:Affinity Labels; D002352:Carrier Proteins; D008565:Membrane Proteins; D033703:Nucleoside Transport Proteins; D013868:Thioinosine; C001789:4-nitrobenzylthioinosine