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首页> 外文期刊>Journal of the Society for Gynecologic Investigation >Serine racemase and D-serine transport in human placenta and evidence for a transplacental gradient for D-serine in humans.
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Serine racemase and D-serine transport in human placenta and evidence for a transplacental gradient for D-serine in humans.

机译：丝氨酸消旋酶和D-丝氨酸在人胎盘中的运输以及人D-丝氨酸在胎盘中的梯度分布的证据。

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OBJECTIVE: To investigate the possible role of human placenta in providing D-serine to the developing fetus. METHODS: Expression of serine racemase in placenta was determined by reverse transcriptase polymerase chain reaction and northern analysis and confirmed by subsequent cloning. The transport of D-serine by human ATB(0) was characterized by expressing the cloned cDNA transiently in mammalian cells using the vaccinia virus expression system. D-serine levels in maternal and fetal blood were measured by fluorescence high-performance liquid chromatography (HPLC) after derivatization of the amino acids with o-phthaldialdehyde and N-tertiary-butyloxycarbonyl-L-cysteine. RESULTS: mRNA for serine racemase was detected in placenta. ATB(0) was capable of d-serine transport, and the transport process is obligatorily dependent on sodium (Na+) with a Na(+):substrate stoichiometry of 1:1 and saturable with a Michaelis-Menten constant of 310 +/- 30 microM. Furthermore, studies have shown that ATB(0) is not expressed in the maternal-facing brush border membrane of human placental syncytiotrophoblast. The circulating concentration of D-serine in maternal serum is 5.8 +/- 0.5 microM, and the corresponding value in the fetal serum is 14.6 +/- 1.2 microM, indicating a two- to three-fold higher concentration of D-serine in the fetus than in the mother. CONCLUSION: We speculate that D-serine is synthesized in human placenta by the racemization of L-serine and that ATB(0), expressed on the basal membrane of the syncytiotrophoblast, mediates the efflux of D-serine into the fetal circulation in exchange for other amino acids in fetal blood.
机译：目的：探讨人胎盘在向发育中的胎儿提供D-丝氨酸中的可能作用。方法：通过逆转录酶聚合酶链反应和Northern分析确定丝氨酸消旋酶在胎盘中的表达，并通过随后的克隆进行证实。通过使用牛痘病毒表达系统在哺乳动物细胞中瞬时表达克隆的cDNA，来表征人ATB（0）对D-丝氨酸的转运。在氨基酸用邻苯二甲醛和N-叔丁氧羰基-L-半胱氨酸衍生化之后，通过荧光高效液相色谱（HPLC）测量母体和胎儿血液中的D-丝氨酸水平。结果：在胎盘中检测到丝氨酸消旋酶的mRNA。 ATB（0）能够进行d-丝氨酸转运，并且转运过程强制性地依赖于钠（Na +），Na（+）：底物化学计量比为1：1，并且其Michaelis-Menten常数为310 +/-即可饱和30微米此外，研究表明，ATB（0）在人胎盘合体滋养层细胞的面向母体的刷状缘膜中未表达。孕妇血清中D-丝氨酸的循环浓度为5.8 +/- 0.5 microM，而胎儿血清中的相应值为14.6 +/- 1.2 microM，这表明孕妇体内D-丝氨酸的浓度高出2到3倍。胎儿比母亲大。结论：我们推测D-丝氨酸是通过L-丝氨酸的外消旋作用在人胎盘中合成的，在合体滋养层细胞基膜上表达的ATB（0）介导D-丝氨酸向胎儿循环的外流，以交换胎儿血液中的其他氨基酸。

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