Ugele Bernhard, St-Pierre Marie V, Pihusch Monika, Bahn Andrew, Hantschmann Peer
I. Frauenklinik Innenstadt and Medizinische Klinik II Grosshadern, Klinikum der Universität München, D-80337 Munich, Germany.
Am J Physiol Endocrinol Metab. 2003 Feb;284(2):E390-8. doi: 10.1152/ajpendo.00257.2002. Epub 2002 Oct 29.
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.
人滋养层细胞依赖外部前体物质的供应来合成雌激素，这些前体物质如硫酸脱氢表雄酮（DHEA-S）和16α-羟基硫酸脱氢表雄酮（16α-OH-DHEA-S）。本研究的目的是表征分离的单核滋养层细胞（MT）对DHEA-S的摄取，并鉴定相关的转运多肽。MT对DHEA-(35)S摄取的动力学分析显示存在一种可饱和的摄取机制（K(m)=26μM，V(max)=428 pmol x mg蛋白(-1) x min(-1)），该机制被一种非饱和摄取机制（扩散常数=1.2μl x mg蛋白(-1) x min(-1)）叠加。MT对[(3)H]DHEA-S的摄取依赖于Na(+)，并受到磺溴酞钠（BSP）、类固醇硫酸盐和丙磺舒的抑制，但不受类固醇葡糖醛酸酯、未结合的类固醇、结合胆汁酸、哇巴因、对氨基马尿酸（PAH）和布美他尼的抑制。MT摄取[(35)S]BSP、[(3)H]硫酸雌酮，但不摄取(3)H标记的哇巴因、雌二醇-17β-葡糖醛酸酯、牛磺胆酸盐和PAH。逆转录聚合酶链反应（RT-PCR）显示，有机阴离子转运多肽OATP-B、-D、-E以及有机阴离子转运体OAT-4高表达，而OATP-A、-C、-8、OAT-3和钠-牛磺胆酸盐共转运多肽（NTCP）在足月胎盘组织以及新鲜分离和培养的滋养层细胞中不表达或仅低表达。孕早期和孕晚期胎盘的免疫组织化学检测发现OAT-4存在于细胞滋养层细胞膜以及合体滋养层细胞的基底表面。我们的结果表明，分离的MT对类固醇硫酸盐的摄取由OATP-B和OAT-4介导，并提示这两种载体蛋白在胎盘摄取胎儿来源的类固醇硫酸盐中具有生理作用。
