Richardson S J, Southwell B R, Jaworowski A
Department of Biochemistry and Molecular Biology, Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Vic., Australia.
Comp Biochem Physiol B Biochem Mol Biol. 2000 Jan;125(1):29-36. doi: 10.1016/s0305-0491(99)00150-9.
The uptake of transferrin by the rat visceral yolk sac membranes, and the fate of this protein, were measured in a two-chambered system which allowed access to both surfaces of these membranes, i.e. that facing the maternal compartment and that facing the fetal compartment. 125I-labeled transferrin was internalized by the maternal surface of the visceral yolk sac but not by the fetal surface. Following internalization, this transferrin was degraded and the amino acids were secreted exclusively towards the fetal compartment. Transcytosis of intact transferrin was not detected in either direction. These results suggest that transport across the rat visceral yolk sac bound to maternally derived transferrin is not a major mechanism of iron transport in vivo. These results support a role for the visceral yolk sac in fetal metabolism, or supplying the fetus with amino acids derived from degradation of specific maternal plasma proteins, in this case, transferrin.
在一个双室系统中测定了大鼠内脏卵黄囊膜对转铁蛋白的摄取以及该蛋白质的去向，该系统可接触到这些膜的两个表面，即面向母体腔室的表面和面向胎儿腔室的表面。125I标记的转铁蛋白被内脏卵黄囊的母体表面内化，但未被胎儿表面内化。内化后，这种转铁蛋白被降解，氨基酸仅向胎儿腔室分泌。未检测到完整转铁蛋白在任何方向的转胞吞作用。这些结果表明，与母体来源的转铁蛋白结合穿过大鼠内脏卵黄囊并非体内铁转运的主要机制。这些结果支持内脏卵黄囊在胎儿代谢中发挥作用，或为胎儿提供源自特定母体血浆蛋白（在这种情况下为转铁蛋白）降解的氨基酸。
