Scrocchi L A, Orava M, Smith C L, Han V K, Hammond G L
Medical Research Council Group in Fetal and Neonatal Health and Development, University of Western Ontario, London, Canada.
Endocrinology. 1993 Feb;132(2):903-9. doi: 10.1210/endo.132.2.7916682.
Glucocorticoids influence fetal development, and their actions are regulated by plasma corticosteroid-binding globulin (CBG). Immunohistochemistry and in situ hybridization were, therefore, used to localize CBG and its mRNA in sections of embryonic and fetal mice and their associated placental tissues from day 5 of gestation until term (day 19). In the fetus, CBG mRNA was first detectable in the hepatocytes on day 11 of gestation. The amount of CBG mRNA in these cells increased transiently to a maximum on days 15-16 of gestation and was negligible by day 19. In hepatocytes, CBG immunoreactivity correlated with the distribution and relative abundance of CBG mRNA. The fetal exocrine pancreas also contained CBG mRNA, but this was only present on days 15-16 of gestation, while immunoreactive CBG persisted in these cells until term. Immunoreactive CBG was detected in the tubular cells of the developing fetal kidney as early as day 13, but CBG mRNA was never found in the fetal kidney, suggesting that the protein is probably sequestered from fetal blood directly or via the glomerular filtrate. The placenta contained immunoreactive CBG throughout gestation, even before its detection in fetal tissues, and it was most abundant in the spongiotrophoblasts and the extracellular matrix surrounding fetal and maternal capillaries. However, CBG mRNA was not detected in the placenta at any gestational age. Therefore, CBG present in the placenta is most likely of maternal origin and may influence the activities of steroid hormones that control placental development and/or function. The presence of smaller immunoreactive polypeptides in placental extracts, compared to CBG in corresponding maternal serum samples, suggests that this process may involve an interaction between maternal CBG and placental proteinases. The results presented here suggest that temporal and spatial changes in the localization of CBG and its mRNA in the fetus may influence the effects of steroid hormones on developing tissues.
糖皮质激素会影响胎儿发育，其作用受血浆皮质类固醇结合球蛋白（CBG）调控。因此，采用免疫组织化学和原位杂交技术，在妊娠第5天直至足月（第19天）的胚胎和胎儿小鼠及其相关胎盘组织切片中定位CBG及其mRNA。在胎儿中，妊娠第11天肝细胞中首次可检测到CBG mRNA。这些细胞中CBG mRNA的量在妊娠第15 - 16天短暂增加至最大值，到第19天可忽略不计。在肝细胞中，CBG免疫反应性与CBG mRNA的分布和相对丰度相关。胎儿外分泌胰腺也含有CBG mRNA，但仅在妊娠第15 - 16天出现，而免疫反应性CBG在这些细胞中持续存在直至足月。早在第13天就在发育中的胎儿肾脏的肾小管细胞中检测到免疫反应性CBG，但在胎儿肾脏中从未发现CBG mRNA，这表明该蛋白可能直接从胎儿血液中或通过肾小球滤过液隔离而来。胎盘在整个妊娠期都含有免疫反应性CBG，甚至在胎儿组织中检测到之前就有，且在海绵滋养层细胞以及胎儿和母体毛细血管周围的细胞外基质中含量最高。然而，在任何胎龄的胎盘中均未检测到CBG mRNA。因此，胎盘中存在的CBG很可能源自母体，可能会影响控制胎盘发育和/或功能的类固醇激素的活性。与相应母体血清样本中的CBG相比，胎盘提取物中存在较小的免疫反应性多肽，这表明该过程可能涉及母体CBG与胎盘蛋白酶之间的相互作用。此处呈现的结果表明，胎儿中CBG及其mRNA定位的时空变化可能会影响类固醇激素对发育中组织的作用。
