Takahashi Y I, Smith J E, Goodman D S
Am J Physiol. 1977 Oct;233(4):E263-72. doi: 10.1152/ajpendo.1977.233.4.E263.
Studies were conducted on the metabolism and placental transport of vitamin A and plasma retinol-binding protein (RBP) during fetal development in the rat. Vitamin A accumulated in the conceptus in three phases: an early phase (days 7-9 of gestation) characterized by a high vitamin A concentration; a second phase (days 11-14) where vitamin A and RBP accumulated in parallel; and a third phase of continued vitamin A and RBP accumulation (days 16-20) in which vitamin A was stored in the fetal liver. The early phase of vitamin A accumulation may reflect a mechanism that exists to prepare the conceptus to meet the presumably higher vitamin A requirements of the critical period (days 10-14) of organ differentiation. Fetuses and placentas from retinol-deficient dams showed low levels of RBP through days 16-18 of gestation. A retinol-repletion study suggested, moreover, that the maternal retinol-RBP complex crossed the placenta. The various studies all suggest that vitamin A is transported from dam to fetus, from and after day 11, mainly by transplacental transport of maternal retinol-RBP. Finally, evidence was obtained indicating that the fetal liver begins to synthesize RBP around the 16th day of gestation and that by the 20th day, the fetal liver has a considerable capacity for RBP synthesis.
对大鼠胎儿发育过程中维生素A和血浆视黄醇结合蛋白（RBP）的代谢及胎盘转运进行了研究。维生素A在孕体中以三个阶段积累：早期阶段（妊娠第7 - 9天），其特征是维生素A浓度较高；第二阶段（第11 - 14天），维生素A和RBP平行积累；第三阶段（第16 - 20天），维生素A和RBP持续积累，其中维生素A储存在胎儿肝脏中。维生素A积累的早期阶段可能反映了一种机制，该机制的存在是为了使孕体做好准备，以满足器官分化关键期（第10 - 14天）可能更高的维生素A需求。来自维生素A缺乏母鼠的胎儿和胎盘在妊娠第16 - 18天显示出低水平的RBP。此外，一项维生素A补充研究表明，母体视黄醇 - RBP复合物可穿过胎盘。各项研究均表明，从妊娠第11天及之后，维生素A主要通过母体视黄醇 - RBP的胎盘转运从母体转运至胎儿。最后，获得的证据表明，胎儿肝脏在妊娠第16天左右开始合成RBP，到第20天时，胎儿肝脏具有相当大的RBP合成能力。
