Schneider H
Department of Obstetrics and Gynecology, University of Berne, Switzerland.
Am J Obstet Gynecol. 1991 Apr;164(4):967-73. doi: 10.1016/0002-9378(91)90567-b.
Bidirectional transport across the placenta provides substrates required for fetal nutrition and prevents accumulation of metabolites in the fetal compartment. Transmission of compounds across the placental barrier occurs by diffusion and carrier-mediated transport. The technique of dual in vitro perfusion of an isolated cotyledon has provided important data for the human placenta. The high degree of permeability for hydrophilic molecules was recently confirmed by in vivo measurements that allow estimates of flux across the human placenta for a number of compounds. The bidirectional nature in transplacental exchange requires asymmetry in flux from the maternal to the fetal side or vice versa, which can be assured by a concentration gradient or an active transport system. There is increasing evidence that placental metabolism with active modification of the composition of nutrients released to the fetus in addition to transport plays an important role.
双向跨胎盘转运提供胎儿营养所需的底物，并防止代谢产物在胎儿体内蓄积。化合物通过扩散和载体介导的转运穿过胎盘屏障。离体子叶双体外灌注技术为人类胎盘提供了重要数据。亲水分子的高通透性最近通过体内测量得到证实，该测量允许估计多种化合物穿过人类胎盘的通量。跨胎盘交换的双向性质要求从母体到胎儿一侧或反之的通量不对称，这可以通过浓度梯度或主动转运系统来保证。越来越多的证据表明，胎盘代谢除了转运外，还对释放到胎儿体内的营养成分进行主动修饰，这起着重要作用。
