Veldman A, Kroos M J, van der Heul C, van Eijk H G
Int J Biochem. 1984;16(1):39-45. doi: 10.1016/0020-711x(84)90048-x.
The mechanism by which iron is transferred from the plasma protein transferrin into erythroid precursors for incorporation in heme is not completely understood. To show a direct functional role of lysosomes in the process of iron uptake we tried to isolate lysosomes from reticulocytes, which have been incubated with 125ITf59Fe. However, with various cell fractionating techniques described for liver cells no pure lysosomes from reticulocytes could be obtained. Fluorescence and electron microscopy showed that reticulocytes hardly contain well-defined lysosomes. There are several indications that in reticulocytes acid vacuoles instead of lysosomes are involved in the removal of iron from endocytosed transferrin. The presence of apoTf, monoferric TfFe(A), monoferric TfFe(B) in the medium after incubation of reticulocytes with diferric transferrin, together with the fact that both iron binding sites of transferrin release their iron at pH present in acid vacuoles, suggests a second mechanism of iron uptake by reticulocytes, in which acid vacuoles are not involved.
铁从血浆蛋白转铁蛋白转移至红系前体细胞并掺入血红素的机制尚未完全明确。为了证明溶酶体在铁摄取过程中具有直接的功能作用，我们尝试从用¹²⁵I标记的转铁蛋白（¹²⁵ITf）与⁵⁹Fe孵育过的网织红细胞中分离溶酶体。然而，采用针对肝细胞描述的各种细胞分级分离技术，均无法从网织红细胞中获得纯溶酶体。荧光显微镜和电子显微镜检查显示，网织红细胞几乎不含明确界定的溶酶体。有多项证据表明，在网织红细胞中，参与从内吞的转铁蛋白中去除铁的是酸性液泡而非溶酶体。网织红细胞与双铁转铁蛋白孵育后，培养基中出现脱铁转铁蛋白（apoTf）、单铁转铁蛋白TfFe(A)和单铁转铁蛋白TfFe(B)，以及转铁蛋白的两个铁结合位点在酸性液泡中的pH值下释放其铁这一事实，提示网织红细胞存在另一种不涉及酸性液泡的铁摄取机制。
