Zaman Z, Heynen M J, Verwilghen R L
Biochim Biophys Acta. 1980 Nov 3;632(4):553-61. doi: 10.1016/0304-4165(80)90332-3.
Mechanism of transferrin iron uptake by rat reticulocytes was studied using 59Fe- and 125I-labelled rat transferrin. Whereas more than 80% of the reticulocyte-bound 59Fe was located in the cytoplasmic fraction, only 25-30% of 125I-labelled transferrin was found inside the cells. As shown by the presence of acetylcholine esterase, 10-15% of the cytoplasmic 125I-labelled transferrin might have been derived from the contamination of this fraction by the plasma membrane fragments. Electron microscopic autoradiography indicated 26% of the cell-bound 125I-labelled transferrin to be inside the reticulocytes. Both the electron microscopic and biochemical studies showed that the rat reticulocytes endocytosed their plasma membrane independently of transferrin. Sepharose-linked transferrin was found to be capable of delivering 59Fe to the reticulocytes. Our results suggest that penetration of the cell membrane by transferrin is not necessary for the delivery of iron and that, although it might make a contribution to the cellular iron uptake, internalization of transferrin reflects endocytotic activity of the reticulocyte cell membrane.
使用59Fe和125I标记的大鼠转铁蛋白研究了大鼠网织红细胞摄取转铁蛋白铁的机制。超过80%与网织红细胞结合的59Fe位于细胞质部分，而在细胞内仅发现25 - 30%的125I标记转铁蛋白。如乙酰胆碱酯酶的存在所示，细胞质中125I标记转铁蛋白的10 - 15%可能源于该部分被质膜碎片污染。电子显微镜放射自显影显示26%与细胞结合的125I标记转铁蛋白在网织红细胞内。电子显微镜和生化研究均表明，大鼠网织红细胞内吞其质膜与转铁蛋白无关。发现琼脂糖结合的转铁蛋白能够将59Fe递送至网织红细胞。我们的结果表明，转铁蛋白穿透细胞膜对于铁的递送并非必要，并且尽管它可能对细胞摄取铁有贡献，但转铁蛋白的内化反映了网织红细胞细胞膜的内吞活性。
