人胎儿各器官组织低密度脂蛋白受体活性的比较

The comparison of activities of low density lipoprotein receptors in human fetal organs and tissues

本文采用组织匀浆^(125)I-LDL特异性结合膜滤过法,测定了5例22～34周龄人胎儿的15种器官与组织LDL受体的活性。结果表明,肾上腺皮质^(125)I-LDL特异性结合(465ng/mg蛋白)活性最高,为其髓质的7倍多。脂肪组织(214ng/mg蛋白)和肝脏(102ng/mg蛋白)的LDL受体活性其次。结合活性较高的组织还有骨骼肌(89ng/mg蛋白)、脑(65ng/mg蛋白)、肾脏(60ng/mg蛋白)及脊髓(56ng/mg蛋白)等。与其他研究者报道不同的是发现人胎儿中枢神经系统LDL受体活性较牛、成人及16～20周龄人胎儿中枢神经系统受体活性为高。^(32)P-cDNA探针杂交分析亦显示人胎儿脑组织中含有较高水平的LDL受体mRNA,提示胎儿中枢神经系统正处于生长发育阶段,故对胆固醇需求较高。另外,本文还初步观察到人胎肝及肾上腺皮质LDL受体活性有随胎龄增加而逐渐升高的趋势。

The activities of low density lipoprotein (LDL) receptors in 15 organs and tissues from 5 human fetuses of the ages of 22 to 34 weeks were determined using a membrane filter assay of the specific binding of ^(125)I-LDL to tissue homogenates. The results showed that the adrenal cortex (465 ng/mg protein) had the highest activity of ^(125)I LDL specific binding seven times than that of the medulla. Adipose tissue (214 ng/mg protein) and liver (102 ng/mg protein) ranked second. Relatively high bindings were also observed in the skeletal muscle (89 ng/mg protein), brain (65 ng/mg protein), kidney (60 ng/mg protein) and spinal cord (56ng/mg protein). It was found that the activity of LDL receptors in the central nervous system of human fetus was higher than that of cows, of human adultsand of humam fetuses of 16 to 20 weeks as reported by other investigators. Relatively high level of LDL receptor mRNA in human fetal brain was also found by ^(32)P-cDNA probe hybridization analysis. It is suggested that the growing and developing central nervous system of human fetus reqiresmore cholesterol. In addition, We also observed preliminarily that the tendency of LDL receptors activities in liver and adrenal gland cortex were gradually inereased with fetal age.