Schenker S, Johnson R F, Hoyumpa A M, Henderson G I
Department of Medicine, University of Texas Health Science Center, San Antonio, TX 78284-7878.
J Lab Clin Med. 1990 Jul;116(1):106-15.
Transport of "physiologic" concentrations of thiamine by the normal, term human placenta was studied by using the perfused cotyledon technique. Thiamine, 50 nmol/L, crossed from the maternal to fetal compartment at a rate somewhat below that of antipyrine, a freely diffusible marker drug. The transport was saturable and inhibited by structural analogues of thiamine, implying participation of carriers. Thiamine accumulated in the fetal compartment against a concentration gradient, suggesting active transport. Consistent with this, transfer of thiamine from the fetal to maternal compartment was significantly lower than in the opposite direction. The vitamin was concentrated in the placenta when compared with maternal and fetal levels. There was no evidence of phosphorylation of thiamine during its transfer. Exposure of the placenta to ethanol, 400 mg/dl, for up to 4 hours did not alter maternal-to-fetal transfer of the vitamin.
采用灌注叶状绒毛膜技术，研究了正常足月人胎盘对“生理”浓度硫胺素的转运情况。50纳摩尔/升的硫胺素从母体向胎儿侧的转运速率略低于安替比林（一种可自由扩散的标记药物）。这种转运具有饱和性，并受到硫胺素结构类似物的抑制，这意味着有载体参与。硫胺素逆浓度梯度在胎儿侧蓄积，提示存在主动转运。与此一致的是，硫胺素从胎儿向母体侧的转运明显低于相反方向。与母体和胎儿水平相比，该维生素在胎盘中富集。在硫胺素转运过程中没有磷酸化的证据。将胎盘暴露于400毫克/分升的乙醇中长达4小时，并未改变该维生素从母体向胎儿的转运。
