The high demand of the fetus for Docosahexaenoic acid, DHA, is satisfied by a concert of several mechanisms that take place in the placental terminal villi. Scarcity of laboratory data makes the detailed description of these mechanisms elusive. Here, the DHA transport across the placenta is modeled as a boundary value problem that accounts for diffusion, reactions with fatty acids binding proteins, FABPs, and metabolic consumption within the Syncytiotrophoblast, ST. For any given DHA fluxes at the bordering membranes, analytical and numerical solutions yield the DHA concentration profile within the ST. We find that in order to comply with adequate DHA delivery to the fetus and with physiological DHA concentrations in the maternal and fetal circulations, it is essential to have a significant rise of DHA concentration at the microvillus membrane, MVM and a rapid dissociation of the DHA from the FABP. The model establishes the relations between the concentrations of the FABPs in the ST, their equilibrium dissociation constant from the DHA, and the placental DHA metabolic degradation rate, hitherto unknown. We conclude that the bound (to the protein) DHA molecule is degraded at a rate of 0.3-0.45 s-1.

中文翻译：

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二十二碳六烯酸通过人类胎盘的运输：一项理论研究。

胎盘末端绒毛中发生的多种机制共同满足了胎儿对二十二碳六烯酸DHA的高需求。实验室数据的匮乏使得对这些机制的详细描述难以捉摸。在这里，DHA跨胎盘的运输被建模为一个边界值问题，该问题说明了扩散，与脂肪酸结合蛋白的反应，FABP和ST在合胞体滋养层中的代谢消耗。对于边界膜上任何给定的DHA通量，分析和数值解可得出ST内DHA的浓度曲线。我们发现，为了符合向胎儿充分输送DHA的要求，并符合母体和胎儿循环中的生理DHA浓度，必须在微绒毛膜上显着提高DHA浓度，MVM和DHA与FABP的快速分离。该模型建立了ST中FABP的浓度，它们与DHA的平衡解离常数以及胎盘DHA代谢降解率（迄今未知）之间的关系。我们得出的结论是，与蛋白质结合的DHA分子以0.3-0.45 s-1的速率降解。