Characterization and identification of steroid sulfate transporters of human placenta

• Published in: American journal of physiology: endocrinology and metabolism 2003-02, Vol.284 (2), p.E390-E398
• Main Authors: Ugele, Bernhard, St-Pierre, Marie V, Pihusch, Monika, Bahn, Andrew, Hantschmann, Peer
• Format: Article
• Language: English
• Subjects: Dehydroepiandrosterone Sulfate - pharmacokinetics; Female; Gene Expression; Humans; Immunohistochemistry; Organic Anion Transporters - genetics; Organic Anion Transporters - metabolism; Organic Anion Transporters, Sodium-Independent - genetics; Organic Anion Transporters, Sodium-Independent - metabolism; Pregnancy; Solute Carrier Organic Anion Transporter Family Member 1b1 - genetics; Solute Carrier Organic Anion Transporter Family Member 1b1 - metabolism; Solute Carrier Organic Anion Transporter Family Member 1B3; Tritium; Trophoblasts - metabolism
• ISSN: 0193-1849; 1522-1555
• DOI: 10.1152/ajpendo.00257.2002

1  I. Frauenklinik Innenstadt and 3  Medizinische Klinik II Großhadern, Klinikum der Universität München, D-80337 Munich; and 4  Zentrum für Physiologie und Pathophysiologie, D-37073 Gottingen, Germany; and 2  Division of Clinical Pharmacology, Department of Internal Medicine, University Hospital, CH-8091 Zürich, Switzerland Human trophoblasts depend on the supply of external precursors, such as dehydroepiandrosterone-3-sulfate (DHEA-S) and 16 -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   µM, V max  = 428 pmol · mg protein 1 · min 1 ), which was superimposed by a nonsaturable uptake mechanism (diffusion constant = 1.2 µl · mg protein 1 · 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-17 -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. estrogen synthesis; isolated trophoblasts; organic anion transporter; dehydroepiandrosterone sulfate