Human placental microvilli contain high-affinity binding sites for folate.
Human placental microvilli contain high-affinity binding sites for folate.
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人胎盘微绒毛含有叶酸的高亲和力结合位点。
DOI：
10.1042/bj2180075
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
H. Ford
中科院分区：
文献类型：
--
作者：
T. Green;H. Ford
研究了从人足月胎盘合体滋养层分离的微绒毛对[~ 3 H]蝶酰谷氨酸[（~ 3 H）PteGlu]的摄取。介质渗透压摩尔浓度变化对[3 H]PteGlu平衡摄取的影响可忽略不计，这表明观察到的摄取代表与微绒毛上或微绒毛内的蛋白质结合，而不是维生素从孵育介质转运至囊内液中的游离状态。平衡摄取实验在广泛的范围内进行的[3 H]PteGlu浓度披露一类的结合位点的关联常数为0.3 nM-1，以及第二类网站具有高容量和低亲和力。在高亲和力位点的[3 H]PteGlu的结合被四氢叶酸和N5-甲基四氢叶酸抑制，但不被其他几种结构类似物抑制。高亲和力结合位点可能是母体血浆叶酸的受体;然而，这些研究中未描述其在胎盘转运或维生素储存中的作用。
Uptake of [3H]pteroylglutamic acid [( 3H]PteGlu) was studied in microvilli isolated from the syncytiotrophoblast of the human term placenta. The effect of changes in medium osmolality on the equilibrium uptake of [3H]PteGlu was negligible, which suggested that the observed uptake represented binding to proteins on or within the microvilli rather than translocation of the vitamin from the incubation medium to a free state in the intravesicular fluid. Equilibrium uptake experiments performed over a wide range of [3H]PteGlu concentrations disclosed a class of binding sites with an association constant of 0.3 nM-1 as well as a second class of sites with high capacity and low affinity. Binding of [3H]PteGlu at the high-affinity sites was inhibited by tetrahydrofolate and N5-methyltetrahydrofolate, but not by several other structural analogues. It is likely that the high-affinity binding sites are receptors for maternal plasma folate; however, their role in placental transport or storage of the vitamin was not delineated in these studies.