Verrijt C E, Kroos M J, van Noort W L, van Eijk H G, van Dijk J P
Department of Chemical Pathology, Erasmus University Rotterdam, The Netherlands.
Placenta. 1997 Jan;18(1):71-7. doi: 10.1016/s0143-4004(97)90073-4.
Transferrin (Tf)-dependent iron transfer from mother to fetus is mediated by Tf receptors (TfRs) which are present on both microvillous and basal membranes of human placental syncytiotrophoblast. We used microvillous and basal membrane vesicles, both isolated from the same human term placenta, to investigate the binding of [125I]-labelled diferric bi-bi antennary tetra-sialo Tf (bb Tf), bi-tri-antennary penta-sialo Tf (bt Tf) and tri-tri-antennary hexa-sialo Tf (tt Tf). To diminish the effect of endogenous Tf, membrane vesicles were washed before binding of [125I]-Tf. The number of TfRs on microvillous membranes was 6.1 +/- 2.4 (mean +/- s.d., n = 15) times higher than that on basal membranes, whereas the affinity of TfRs on basal membranes was 3.9 +/- 0.4 (mean +/- s.d., n = 15) times higher than that of TfRs on microvillous membranes, irrespective the isoTf used. The affinity constants of TfRs on both microvillous and basal membranes were higher for bb Tf than for bt Tf and higher for bt Tf than for tt Tf. However, these latter differences were rather small and probably not of physiological importance.
转铁蛋白（Tf）介导的铁从母体向胎儿的转运是由转铁蛋白受体（TfRs）介导的，该受体存在于人类胎盘合体滋养层细胞的微绒毛膜和基底膜上。我们使用从同一足月人胎盘分离的微绒毛膜和基底膜囊泡，来研究[125I]标记的双铁双触角四唾液酸转铁蛋白（bb Tf）、双三触角五唾液酸转铁蛋白（bt Tf）和三三触角六唾液酸转铁蛋白（tt Tf）的结合情况。为了减少内源性Tf的影响，在[125I]-Tf结合之前对膜囊泡进行洗涤。微绒毛膜上TfRs的数量比基底膜上的高6.1±2.4（平均值±标准差，n = 15）倍，而基底膜上TfRs的亲和力比微绒毛膜上的TfRs高3.9±0.4（平均值±标准差，n = 15）倍，无论使用哪种同种Tf。bb Tf在微绒毛膜和基底膜上TfRs的亲和常数均高于bt Tf，bt Tf的亲和常数高于tt Tf。然而，后两者的差异相当小，可能没有生理重要性。
