Transport of the placental estriol precursor 16α-hydroxy-dehydroepiandrosterone sulfate (16α-OH-DHEAS) by stably transfected OAT4-, SOAT-, and NTCP-HEK293 cells.
16α-Hydroxy-dehydroepiandrosterone sulfate (16α-OH-DHEAS) mainly originates from the fetus and serves as precursor for placental estriol biosynthesis. For conversion of 16α-OH-DHEAS to estriol several intracellular enzymes are required. However, prior to enzymatic conversion, 16α-OH-DHEAS must enter the cells by carrier mediated transport. To identify these carriers, uptake of 16α-OH-DHEAS by the candidate carriers organic anion transporter OAT4, sodium-dependent organic anion transporter SOAT, Na(+)-taurocholate cotransporting polypeptide NTCP, and organic anion transporting polypeptide OATP2B1 was measured in stably transfected HEK293 cells by LC-MS-MS. Furthermore, the study aimed to localize SOAT in the human placenta. Stably transfected OAT4-HEK293 cells revealed a partly sodium-dependent transport for 16α-OH-DHEAS with an apparent Km of 23.1 ± 5.1 μM and Vmax of 485.0 ± 39.1 pmol/mg protein/min, while stably transfected SOAT- and NTCP-HEK293 cells showed uptake only under sodium conditions with Km of 319.0 ± 59.5 μM and Vmax of 1465.8 ± 118.8 pmol/mg protein/min for SOAT and Km of 51.4 ± 9.9 μM and Vmax of 1423.3 ± 109.6 pmol/mg protein/min for NTCP. In contrast, stably transfected OATP2B1-HEK293 cells did not transport 16α-OH-DHEAS at all. Immunohistochemical studies and in situ hybridization of formalin fixed and paraffin embedded sections of human late term placenta showed expression of SOAT in syncytiotrophoblasts, predominantly at the apical membrane as well as in the vessel endothelium. In conclusion, OAT4, SOAT, and NTCP were identified as carriers for the estriol precursor 16α-OH-DHEAS. At least SOAT and OAT4 seem to play a functional role for the placental estriol synthesis as both are expressed in the syncytiotrophoblast of human placenta.
Institute of Pharmacology and Toxicology, Justus Liebig University of Giessen, 35392 Giessen, Germany.
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Schweigmann
Steroid Research & Mass Spectrometry Unit, Division of Pediatric Endocrinology and Diabetology, Center of Child and Adolescent Medicine, Justus Liebig University of Giessen, 35392 Giessen, Germany.
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Sánchez-Guijo
University Hospital, Ludwig Maximilians University of Munich, 80337 Munich, Germany.
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Ugele
Institute of Veterinary Anatomy, Histology and Embryology, Justus Liebig University of Giessen, 35392 Giessen, Germany.
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Hartmann
Steroid Research & Mass Spectrometry Unit, Division of Pediatric Endocrinology and Diabetology, Center of Child and Adolescent Medicine, Justus Liebig University of Giessen, 35392 Giessen, Germany.
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Hartmann
Institute of Veterinary Anatomy, Histology and Embryology, Justus Liebig University of Giessen, 35392 Giessen, Germany.
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Bergmann
Department of Anatomy, University of Veterinary Medicine, 30173 Hannover, Germany.
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Pfarrer
Institute of Pharmacology and Toxicology, Justus Liebig University of Giessen, 35392 Giessen, Germany.
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Döring
Steroid Research & Mass Spectrometry Unit, Division of Pediatric Endocrinology and Diabetology, Center of Child and Adolescent Medicine, Justus Liebig University of Giessen, 35392 Giessen, Germany.
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Wudy
Institute of Pharmacology and Toxicology, Justus Liebig University of Giessen, 35392 Giessen, Germany.
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Petzinger
Institute of Pharmacology and Toxicology, Justus Liebig University of Giessen, 35392 Giessen, Germany.
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Geyer
Institute of Pharmacology and Toxicology, Justus Liebig University of Giessen, 35392 Giessen, Germany. Electronic address: gary.grosser@vetmed.uni-giessen.de.
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Grosser
D001692:Biological Transport; D015153:Blotting, Western; D002853:Chromatography, Liquid; D003687:Dehydroepiandrosterone / Q000031:analogs & derivatives* / Q000378:metabolism; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D027361:Organic Anion Transporters / Q000235:genetics / Q000378:metabolism*; D029363:Organic Anion Transporters, Sodium-Dependent / Q000235:genetics / Q000378:metabolism*; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics; D002785:Sterol O-Acyltransferase / Q000235:genetics / Q000378:metabolism*; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D014162:Transfection; D014327:Trophoblasts / Q000378:metabolism*
D027361:Organic Anion Transporters; D029363:Organic Anion Transporters, Sodium-Dependent; D012333:RNA, Messenger; D027981:Symporters; C011277:16-hydroxydehydroepiandrosterone; C071908:sodium-bile acid cotransporter; D003687:Dehydroepiandrosterone; D002785:Sterol O-Acyltransferase; C493492:sterol O-acyltransferase 1
DHEAS; OAT4; Placenta; SOAT; Steroid sulfate; Transport