Characterization and identification of steroid sulfate transporters of human placenta.
Human trophoblasts depend on the supply of external precursors, such as dehydroepiandrosterone-3-sulfate (DHEA-S) and 16 alpha-OH-DHEA-S, for synthesis of estrogens. The aim of the present study was to characterize the uptake of DHEA-S by isolated mononucleated trophoblasts (MT) and to identify the involved transporter polypeptides. The kinetic analysis of DHEA-(35)S uptake by MT revealed a saturable uptake mechanism (K(m) = 26 microM, V(max) = 428 pmol x mg protein(-1) x min(-1)), which was superimposed by a nonsaturable uptake mechanism (diffusion constant = 1.2 microl x mg protein(-1) x min(-1)). Uptake of [(3)H]DHEA-S by MT was Na(+) dependent and inhibited by sulfobromophthalein (BSP), steroid sulfates, and probenecid, but not by steroid glucuronides, unconjugated steroids, conjugated bile acids, ouabain, p-aminohippurate (PAH), and bumetanide. MT took up [(35)S]BSP, [(3)H]estrone-sulfate, but not (3)H-labeled ouabain, estradiol-17beta-glucuronide, taurocholate, and PAH. RT-PCR revealed that the organic anion-transporting polypeptides OATP-B, -D, -E, and the organic anion transporter OAT-4 are highly expressed, and that OATP-A, -C, -8, OAT-3, and Na(+)-taurocholate cotransporting polypeptide (NTCP) are not or are only lowly expressed in term placental tissue and freshly isolated and cultured trophoblasts. Immunohistochemistry of first- and third-trimester placenta detected OAT-4 on cytotrophoblast membranes and at the basal surface of the syncytiotrophoblast. Our results indicate that uptake of steroid sulfates by isolated MT is mediated by OATP-B and OAT-4 and suggest a physiological role of both carrier proteins in placental uptake of fetal-derived steroid sulfates.
Ugele
Bernhard
B
I. Frauenklinik Innenstadt and Medizinische Klinik II Grosshadern, Klinikum der Universität München, D-80337 Munich, Germany. ugele@helios.med.uni-muenchen.de
St-Pierre
Marie V
MV
Pihusch
Monika
M
Bahn
Andrew
A
Hantschmann
Peer
P
D019314:Dehydroepiandrosterone Sulfate / Q000493:pharmacokinetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D027381:Liver-Specific Organic Anion Transporter 1 / Q000235:genetics / Q000378:metabolism; D027361:Organic Anion Transporters / Q000235:genetics* / Q000378:metabolism*; D029362:Organic Anion Transporters, Sodium-Independent / Q000235:genetics / Q000378:metabolism; D011247:Pregnancy; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3; D014316:Tritium; D014327:Trophoblasts / Q000378:metabolism*
D027381:Liver-Specific Organic Anion Transporter 1; D027361:Organic Anion Transporters; D029362:Organic Anion Transporters, Sodium-Independent; C427207:SLC22A11 protein, human; C421209:SLCO1B3 protein, human; C450859:SLCO2B1 protein, human; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3; C114338:organic anion transport protein 3; D014316:Tritium; D019314:Dehydroepiandrosterone Sulfate