Campbell F M, Gordon M J, Dutta-Roy A K
Rowett Research Institute, Aberdeen, Scotland, United Kingdom.
Mol Cell Biochem. 1996 Feb 9;155(1):77-83. doi: 10.1007/BF00714336.
Fatty acid uptake by the placenta is thought to be a carrier-mediated process, however the mechanism by which long chain polyunsaturated fatty acids (LCPUFA) are preferentially accumulated from the maternal circulation to the fetal tissues is still unclear. To examine the role of the placenta in this process, binding of four different radiolabelled fatty acids (-14C-oleate, -14C-linoleate, [14C]a-linolenate and [14C]arachidonate) to human placental membranes was studied. Binding of fatty acid was found to be time- and temperature dependent. At equilibrium, the total binding of oleate was highest (5.1 +/- 0.1 nmoles/mg protein) followed by linoleate (2.8 +/- 0.31 nmoles/mg protein) and arachidonate (2.06 +/- 0.4 nmoles/mg protein) and alpha-linolenate binding was lowest (0.5 +/- 0.1 nmoles/mg protein). However, oleate had the lowest specific binding (37% of the total binding) whereas arachidonate had the highest specific binding (approximately 86% of the total binding) followed by linoleate and a-linolenate (62%, and 69% of the total binding, respectively). Binding of each [14C] fatty acid was also assessed in the presence of 20-fold excess of other unlabelled ligands. Binding sites seem to have preference for the binding of [14C] fatty acids in the following order: arachidonic acid >>> linoleic acid >> a-linolenic acid >>>>> oleic acid, whereas BSP and a-tocopherol did not show any competition with any of the [14C] fatty acids. These data suggest that the fatty acid binding sites in placental membranes are specific for the fatty acids but that they have heterogeneous affinities. Trans fatty acids (elaidic and linoelaidic acids) also competed very strongly for the [14C] fatty acid binding. Polyclonal antiserum raised against placental FABPpm inhibited binding of these [14C] fatty acids but with variable degrees of inhibition; EFA/LCPUFA binding was much more than that of oleate. Our data suggest that EFA/LCPUFA bound to albumin are preferentially transported by human placental membranes and that the placental FABPpm may be involved in the sequestration of EFA/LCPUFA by the placenta.
胎盘对脂肪酸的摄取被认为是一个载体介导的过程，然而长链多不饱和脂肪酸（LCPUFA）从母体循环优先积累到胎儿组织的机制仍不清楚。为了研究胎盘在此过程中的作用，研究了四种不同放射性标记脂肪酸（-14C-油酸、-14C-亚油酸、[14C]α-亚麻酸和[14C]花生四烯酸）与人胎盘膜的结合。发现脂肪酸的结合具有时间和温度依赖性。在平衡时，油酸的总结合量最高（5.1±0.1纳摩尔/毫克蛋白质），其次是亚油酸（2.8±0.31纳摩尔/毫克蛋白质）和花生四烯酸（2.06±0.4纳摩尔/毫克蛋白质），α-亚麻酸的结合量最低（0.5±0.1纳摩尔/毫克蛋白质）。然而，油酸的特异性结合最低（占总结合量的37%），而花生四烯酸的特异性结合最高（约占总结合量的86%），其次是亚油酸和α-亚麻酸（分别占总结合量的62%和69%）。在存在20倍过量的其他未标记配体的情况下，还评估了每种[14C]脂肪酸的结合。结合位点似乎对[14C]脂肪酸的结合具有以下偏好顺序：花生四烯酸>>>亚油酸>>α-亚麻酸>>>>油酸，而溴磺酚酞（BSP）和α-生育酚与任何一种[14C]脂肪酸均未表现出竞争。这些数据表明，胎盘膜中的脂肪酸结合位点对脂肪酸具有特异性，但它们具有不同的亲和力。反式脂肪酸（反油酸和反亚油酸）对[14C]脂肪酸结合的竞争也非常强烈。针对胎盘脂肪酸结合蛋白（FABPpm）产生的多克隆抗血清抑制了这些[14C]脂肪酸的结合，但抑制程度不同；必需脂肪酸/长链多不饱和脂肪酸的结合比油酸的结合受抑制程度大得多。我们的数据表明，与白蛋白结合的必需脂肪酸/长链多不饱和脂肪酸优先被人胎盘膜转运，并且胎盘FABPpm可能参与胎盘对必需脂肪酸/长链多不饱和脂肪酸的隔离。
