Development and polarization of cationic amino acid transporters and regulators in the human placenta.
We have investigated L-arginine transport systems in the human placental syncytiotrophoblast across gestation using purified microvillous (MVM) and basal (BM) plasma membrane vesicles. In MVM from first-trimester and term placentas, L-arginine transport was by systems y(+) and y(+)L. In BM (term placentas), however, there was evidence for system y(+)L only. The Michaelis constant of system y(+)L was significantly lower (P < 0.05) in first-trimester compared with term MVM and lower in term MVM compared with BM (P < 0.05). There was no functional evidence for system b(0+) in term MVM or BM. Cationic amino acid transporter (CAT) 1, CAT 4, and 4F2hc were detected using RT-PCR in placentas throughout gestation. rBAT was not detected in term placentas. An approximately 85-kDa and an approximately 135-kDa protein was detected by Western blotting in MVM under reducing and nonreducing conditions, respectively, consistent with the 4F2hc monomer and the 4F2hc-light chain dimer, and their expression was significantly higher (P < 0.05) in term compared with first-trimester MVM. These proteins were not detected in BM despite functional evidence for system y(+)L. These data suggest different roles for 4F2hc in the development and polarization of cationic amino acid transporters in the syncytiotrophoblast.
Ayuk
P T
PT
Academic Unit of Child Health, University of Manchester and Department of Obstetrics and Gynecology, St. Mary's Hospital, Manchester M13 0JH, United Kingdom.
Sibley
C P
CP
Donnai
P
P
D'Souza
S
S
Glazier
J D
JD
D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids / Q000378:metabolism / Q000494:pharmacology; D015703:Antigens, CD / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002824:Chorionic Villi / Q000502:physiology*; D036861:Delivery, Obstetric; D005260:Female; D027261:Fusion Regulatory Protein-1; D005786:Gene Expression Regulation; D006801:Humans; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D010920:Placenta / Q000502:physiology*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014327:Trophoblasts / Q000502:physiology*
D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids; D015703:Antigens, CD; D002352:Carrier Proteins; D027261:Fusion Regulatory Protein-1; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C499489:SLC7A9 protein, human