Gérard B, Farman N, Raja K B, Eugène E, Grandchamp B, Beaumont C
INSERM U409, Institut Fédératif de Recherches Cellules Epithéliales,Faculté Xavier Bichat, Paris, France.
Exp Cell Res. 1996 Oct 10;228(1):8-13. doi: 10.1006/excr.1996.0292.
Regulation of iron absorption occurs mainly at the level of duodenal enterocytes. Several proteins including ferritin, the iron-storing molecule, have been implicated in the uptake, cellular processing, and transfer of iron by the mucosal cells. H and L ferritin subunits assemble in various proportions to form a 24-subunit protein shell which can store up to 4500 iron atoms. Although tissue-specific distribution of H and L ferritin mRNAs has been widely described, little is known of ferritin gene expression in duodenal cells. In this study, we performed quantitative measurements of H and L ferritin mRNAs levels in mouse duodenum, ileum, and liver by ribonuclease protection assay. In addition, we assessed the relative subcellular distribution of these two mRNAs in mouse duodenal and ileal sections by in situ hybridization. The results show that in duodenal cells, the level of H ferritin mRNA is higher than the L ferritin level (H/L ratio of about 5). Moreover, expression of the H mRNA is regulated along both axes of the small intestine: the level increases sharply from the crypt to the apex of the villus, thus following the general differentiation pathway of these cells, and decreases from the proximal to the distal small intestine. In contrast, the L ferritin mRNA level does not change along the cryptovillus axis and increases in value in the ileum. These results suggest that expression of the H ferritin gene is dependent on the differentiation of the enterocytes but, as yet, the regulatory elements remain to be identified.
铁吸收的调节主要发生在十二指肠肠上皮细胞水平。包括铁储存分子铁蛋白在内的几种蛋白质与黏膜细胞对铁的摄取、细胞内加工及转运有关。H和L铁蛋白亚基以不同比例组装形成一个可储存多达4500个铁原子的24亚基蛋白壳。尽管H和L铁蛋白mRNA的组织特异性分布已被广泛描述，但对十二指肠细胞中铁蛋白基因表达了解甚少。在本研究中，我们通过核糖核酸酶保护试验对小鼠十二指肠、回肠和肝脏中H和L铁蛋白mRNA水平进行了定量测定。此外，我们通过原位杂交评估了这两种mRNA在小鼠十二指肠和回肠切片中的相对亚细胞分布。结果显示，在十二指肠细胞中，H铁蛋白mRNA水平高于L铁蛋白水平（H/L比值约为5）。而且，H mRNA的表达沿小肠的两个轴受到调节：从隐窝到绒毛顶端水平急剧升高，因此遵循这些细胞的一般分化途径，并且从近端小肠到远端小肠降低。相反，L铁蛋白mRNA水平沿隐窝 - 绒毛轴没有变化，在回肠中其值升高。这些结果表明，H铁蛋白基因的表达依赖于肠上皮细胞的分化，但调控元件尚未确定。
