Soprano D R, Soprano K J, Goodman D S
Proc Natl Acad Sci U S A. 1986 Oct;83(19):7330-4. doi: 10.1073/pnas.83.19.7330.
Studies were conducted to explore the synthesis of retinol-binding protein and transthyretin by embryonic and extraembryonic tissues during fetal development in the rat. The levels of retinol-binding protein mRNA and transthyretin mRNA were measured in fetal liver and in extraembryonic tissues by RNA gel blot analysis and hybridization with specific cDNA probes. Retinol-binding protein mRNA and transthyretin mRNA were both detected in the liver of fetuses at 14 days of gestation. The relative levels of these two transcripts increased during later fetal development; by the 20th day of gestation retinol-binding protein mRNA levels were comparable to those of the adult liver, while the levels of transthyretin mRNA were only 46% of those of the adult liver. Examination of the extraembryonic membranes for retinol-binding protein mRNA and transthyretin mRNA showed that these two transcripts were present specifically and only in the visceral yolk sac. The relative levels of retinol-binding protein mRNA and transthyretin mRNA in visceral yolk sac were constant from 14 to 20 days of gestation, averaging 58% and 51%, respectively, of the adult liver levels of these two transcripts. Both retinol-binding protein mRNA and transthyretin mRNA in the visceral yolk sac were found to be specifically localized in the endodermal layer. Finally, both immunoprecipitable retinol-binding protein and transthyretin were found to be synthesized and secreted by explant cultures of visceral yolk sac tissue. These data show that the visceral yolk sac is a major source of both retinol-binding protein and transthyretin in the developing fetus. Since the visceral yolk sac is a site of true placentation and nutrient transfer in the rodent, this raises the possibility that visceral yolk sac-derived retinol-binding protein and transthyretin may play important roles in the transport and delivery of retinol from the maternal blood to the developing fetus.
开展了多项研究，以探索大鼠胎儿发育过程中胚胎组织和胚外组织对视黄醇结合蛋白和转甲状腺素蛋白的合成情况。通过RNA凝胶印迹分析以及与特异性cDNA探针杂交，测定了胎儿肝脏和胚外组织中视黄醇结合蛋白mRNA和转甲状腺素蛋白mRNA的水平。在妊娠14天时，在胎儿肝脏中检测到了视黄醇结合蛋白mRNA和转甲状腺素蛋白mRNA。在胎儿后期发育过程中，这两种转录本的相对水平均有所增加；到妊娠第20天时，视黄醇结合蛋白mRNA水平与成年肝脏相当，而转甲状腺素蛋白mRNA水平仅为成年肝脏的46%。对胚外膜中的视黄醇结合蛋白mRNA和转甲状腺素蛋白mRNA进行检测发现，这两种转录本仅特异性存在于内脏卵黄囊中。在内脏卵黄囊中，视黄醇结合蛋白mRNA和转甲状腺素蛋白mRNA的相对水平在妊娠14至20天期间保持恒定，分别平均为成年肝脏中这两种转录本水平的58%和51%。在内脏卵黄囊中，视黄醇结合蛋白mRNA和转甲状腺素蛋白mRNA均特异性定位于内胚层。最后，发现内脏卵黄囊组织的外植体培养物能够合成并分泌可免疫沉淀的视黄醇结合蛋白和转甲状腺素蛋白。这些数据表明，内脏卵黄囊是发育中胎儿视黄醇结合蛋白和转甲状腺素蛋白的主要来源。由于内脏卵黄囊是啮齿动物真正的胎盘形成和营养物质转运部位，这增加了一种可能性，即内脏卵黄囊来源的视黄醇结合蛋白和转甲状腺素蛋白可能在将视黄醇从母体血液转运并递送至发育中胎儿的过程中发挥重要作用。
