Zeller U, Kuhn H J
Abteilung Morphologie des Zentrums Anatomie, Universität Göttingen, Germany.
J Anat. 1994 Jun;184 ( Pt 3)(Pt 3):597-606.
Tree shrews (Tupaia belangeri) develop a bidiscoid endotheliochorial placenta. In addition, histiotrophe secreted by uterine glands is absorbed by the paraplacental trophoblast. Histiotrophe which is rich in iron is necessary for erythropoiesis in the young embryo. This report is part of a study of the accumulation and metabolism of iron in the endometrium of precisely dated pregnant Tupaia belangeri by application of electron spectroscopy and histochemistry. In the endometrium of tree shrews which had been pregnant at least once, iron-laden granules were present in macrophages and secreting cells of uterine glands. Iron accumulated in the endometrium shortly after parturition, when macrophages phagocytosed erythrocytes at small haematomas 0.2-0.5 mm in diameter. These haematomas arose during parturition after bleeding into the uterine stroma when the placental discs were detached. At 24 h after parturition the following structural consequences of the erythrolysosomal breakdown of phagocytosed erythrocytes could be observed: free cytosolic siderin granules, membrane-bound siderosomes, telolysosomes (some of which contained myelin figures or lipid droplets) and mixed telolysosomes (containing membranous stacks and siderin granules). During the lysosomal degradation of phagocytosed erythrocytes, iron was transferred from haemoglobin into a different macromolecular compound. Electron energy loss spectra detected from inside siderosomes indicated an iron-oxygen compound, and high-power bright field electron micrographs of siderosomes demonstrated the ultrastructural pattern characteristic of ferritin. At about d 12 of a new pregnancy, macrophages containing siderosomes closely approached the bases of secreting cells of endometrial glands. This strongly suggests that iron is transferred from the macrophages to the glandular cells. Within the glandular cells, iron-rich histiotrophe was synthesised and released into the glandular lumen. Within the uterine cavity this histiotrophe was absorbed by the omphalopleure. We suggest that among eutherians, postpartum erythrophagocytosis, the transfer of iron from macrophages to uterine glands, and the paraplacental uptake of iron, represent an ancestral mechanism of iron supply to the embryo.
树鼩（Tupaia belangeri）发育出双盘内皮绒毛膜胎盘。此外，子宫腺分泌的组织营养物质被胎盘旁滋养层吸收。富含铁的组织营养物质对幼胚的红细胞生成是必需的。本报告是通过应用电子能谱和组织化学对精确计时的怀孕树鼩子宫内膜中铁的积累和代谢进行研究的一部分。在至少怀孕过一次的树鼩子宫内膜中，巨噬细胞和子宫腺分泌细胞中存在含铁颗粒。分娩后不久，当巨噬细胞吞噬直径为0.2 - 0.5毫米的小血肿中的红细胞时，铁在子宫内膜中积累。这些血肿是在胎盘盘分离时子宫基质出血后分娩期间出现的。分娩后24小时，可以观察到吞噬红细胞的红细胞溶酶体分解的以下结构后果：游离的胞质铁蛋白颗粒、膜结合的铁体、终末溶酶体（其中一些含有髓鞘样结构或脂滴）和混合终末溶酶体（含有膜性堆叠物和铁蛋白颗粒）。在吞噬红细胞的溶酶体降解过程中，铁从血红蛋白转移到一种不同的大分子化合物中。从铁体内检测到的电子能量损失谱表明存在铁 - 氧化合物，铁体的高倍明场电子显微照片显示了铁蛋白特有的超微结构模式。在新怀孕约第12天时，含有铁体的巨噬细胞紧密靠近子宫内膜腺分泌细胞的基部。这强烈表明铁从巨噬细胞转移到腺细胞。在腺细胞内，富含铁的组织营养物质被合成并释放到腺腔中。在子宫腔内，这种组织营养物质被脐胸膜吸收。我们认为，在真兽类动物中，产后红细胞吞噬作用、铁从巨噬细胞向子宫腺的转移以及胎盘旁对铁的摄取，代表了向胚胎供应铁的一种原始机制。
