Distribution and transfer pathways of antioxidant molecules inside the first trimester human gestational sac

The first-trimester human placenta has limited antioxidant enzyme capacity. We investigated the distribution and transfer pathways of antioxidant molecules inside the first trimester gestational sac. The coelomic fluid of the exocoelomic cavity, which borders the inside of the first-trimester placenta, contained a very low level of reduced glutathione. Glutathione disulfide was undetectable in most coelomic samples, suggesting that the role of glutathione-related detoxification system is limited in fetal fluid compartments. The coelomic fluid contained similar concentrations of ascorbic and uric acid to maternal plasma. The levels of alpha- and gamma-tocopherol were lower in coelomic fluid, compared with maternal plasma. The presence of these molecules inside the early gestational sac suggests that they may play an essential role in the fetal tissues' antioxidant capacity at a time when the fetus is most vulnerable to oxidative stress. We also demonstrated by immunostaining the presence of alpha-tocopherol transfer protein in the cytoplasm of trophoblastic cells, glandular epithelium of the decidua, and mesothelial layer of the secondary yolk sac. This finding indicates that the uterine glands and the secondary yolk sac play key roles in supplying this essential vitamin to the developing fetus before the placental circulations are established.