TRANSPLACENTAL TRANSPORT OF LEAD
TRANSPLACENTAL TRANSPORT OF LEAD
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DOI：
10.2307/3430905
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发表时间：
1990-11-01
影响因子：
10.4
通讯作者：
GOYER, RA
中科院分区：
文献类型：
--
作者：
GOYER, RA
神经毒性是婴儿和幼儿接触铅的主要健康影响，目前人们担心铅对子宫内儿童可能产生的毒性影响。 铅转运没有胎盘-胎儿屏障。 母亲和胎儿的血铅水平几乎相同，因此铅可以不受阻碍地通过胎盘。 早在前三个月（13周）结束时，就已经测量了胎儿大脑中的铅含量。 在一般人群中，母亲的胎儿在整个怀孕期间的大脑大小和铅含量的增加率相似，因此，除非母亲的暴露发生变化，否则在怀孕期间铅的浓度可能不会有很大差异。 然而，胎儿越年轻，细胞对铅毒性效应的敏感性可能越大。 铅对神经系统的毒性表现为由于毛细血管内皮细胞的渗透性改变而引起的脑水肿或肿胀。 实验研究表明，形成发育中大脑毛细血管的未成熟内皮细胞对铅的影响抵抗力较低，允许包括铅在内的液体和阳离子到达大脑新形成的组成部分，特别是星形胶质细胞和神经元。 此外，星形胶质细胞和神经元以铅蛋白复合物的形式螯合铅的能力只发生在胎儿发育的后期，允许成熟脑细胞中的铅与重要的亚细胞器，特别是线粒体相互作用，线粒体是主要的细胞能量来源。 细胞内铅也影响钙的结合位点，这反过来又可能影响许多细胞功能，包括神经递质的释放。
Neurotoxicity is the major health effect from exposure to lead for infants and young children, and there is current concern regarding possible toxic effects of lead on the child while in utero. There is no placental-fetal barrier to lead transport. Maternal and fetal blood lead levels are nearly identical, so lead passes through the placenta unencumbered. Lead has been measured in the fetal brain as early as the end of the first trimester (13 weeks). There is a similar rate of increase in brain size and lead content throughout pregnancy in the fetus of mothers in the general population, so concentration of lead probably does not differ greatly during gestation unless exposure of the mother changes. Cell-specific sensitivity to the toxic effects of lead, however, may be greater the younger the fetus. Lead toxicity to the nervous system is characterized by edema or swelling of the brain due to altered permeability of capillary endothelial cells. Experimental studies suggest that immature endothelial cells forming the capillaries of the developing brain are less resistant to the effects of lead, permitting fluid and cations including lead to reach newly formed components of the brain, particularly astrocytes and neurons. Also, the ability of astrocytes and neurons to sequester lead in the form of lead protein complexes occurs only in the later stages of fetal development, permitting lead in maturing brain cells to interact with vital subcellular organelles, particularly mitochondria, which are the major cellular energy source. Intracellular lead also affects binding sites for calcium which, in turn, may affect numerous cell functions including neurotransmitter release.