Sorokin L M, Morgan E H, Yeoh G C
J Cell Physiol. 1987 Jun;131(3):342-53. doi: 10.1002/jcp.1041310306.
The mechanism of iron uptake and the changes which occur during cellular development of muscle cells were investigated using primary cultures of chick embryo breast muscle. Replicating presumptive myoblasts were examined in exponential growth and after growth had plateaued. These were compared to the terminally differentiated cell type, the myotube. All cells, regardless of the state of growth or differentiation, had specific receptors for transferrin. Presumptive myoblasts in exponential growth had more transferrin receptors (3.78 +/- 0.24 X 10(10) receptors/micrograms DNA) than when division had ceased (1.70 +/- 0.14 X 10(10) receptors/micrograms DNA), while myotubes had 3.80 +/- 0.26 X 10(10) receptors/micrograms DNA. Iron uptake occurred by receptor-mediated endocytosis of transferrin. While iron was accumulated by the cells, apotransferrin was released in an undegraded form. There was a close correlation between the molar rates of endocytosis of transferrin and iron. Maximum rates of iron uptake were significantly higher in myotubes than in presumptive myoblasts in either exponential growth or after growth had plateaued. There were two rates of exocytosis of transferrin, implying the existence of two intracellular pathways for transferrin. These experiments demonstrate that iron uptake by muscle cells in culture occurs by receptor-mediated endocytosis of transferrin and that transferrin receptor numbers and the kinetics of transferrin and iron uptake vary with development of the cells.
利用鸡胚胸肌原代培养物研究了铁摄取机制以及肌肉细胞在细胞发育过程中发生的变化。对处于指数生长期和生长达到平台期后的假定成肌细胞进行了检查。将这些细胞与终末分化的细胞类型即肌管进行了比较。所有细胞,无论生长或分化状态如何,都有转铁蛋白的特异性受体。处于指数生长期的假定成肌细胞比分裂停止时具有更多的转铁蛋白受体(3.78±0.24×10¹⁰受体/微克DNA),而分裂停止时为(1.70±0.14×10¹⁰受体/微克DNA),而肌管具有3.80±0.26×10¹⁰受体/微克DNA。铁的摄取是通过转铁蛋白的受体介导的内吞作用发生的。当细胞积累铁时,脱铁转铁蛋白以未降解的形式释放。转铁蛋白和铁的内吞摩尔速率之间存在密切相关性。在指数生长期或生长达到平台期后,肌管中铁摄取的最大速率显著高于假定成肌细胞。转铁蛋白有两种胞吐速率,这意味着存在两条转铁蛋白的细胞内途径。这些实验表明,培养的肌肉细胞中铁的摄取是通过转铁蛋白的受体介导的内吞作用发生的,并且转铁蛋白受体数量以及转铁蛋白和铁摄取的动力学随细胞发育而变化。