Pérez G, Garbossa G, Sassetti B, Di Risio C, Nesse A
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
J Inorg Biochem. 1999 Aug 30;76(2):105-12. doi: 10.1016/s0162-0134(99)00121-x.
It has been suggested that aluminium (Al) has a deleterious effect on erythropoiesis. However, there is still uncertainty as to its action mechanism. The present work was designed to determine how Al could affect the iron (Fe) metabolism in the human erythroleukaemia cell line K562. These cells, that express surface transferrin receptors (TfRs), were induced to erythroid differentiation by either haemin or hydroxyurea in 72 h cultures in media containing apotransferrin (apoTf). In the presence of aluminium citrate, the number of benzidine-positive cells decreased 18% when the cultures were induced by haemin, and 30% when hydroxyurea was the inducer. Cell viability was always unaffected. From competition assays, surface binding of 125I-Tf-Fe2 was found to be inversely related (p < 0.05) to Tf-Al2 concentration (from 2.5 to 10 nM). The dissociation constants (Kd) of the binding reaction between TfRs and the ligands Tf-Fe2 and Tf-Al2 were calculated. Kd values of the same order of magnitude demonstrated that TfR has a similar affinity for Tf-Fe2 (Kd = 1.75 x 10(-9) M) and Tf-Al2 (Kd = 1.37 x 10(-9) M). The number of surface TfRs, measured by kinetic 125I-Tf-Fe2 binding assays, was higher in induced cells cultured in the presence of Al. Nevertheless, in spite of the inhibition of cell haemoglobinization observed, 59Fe incorporation values were not different from those measured in control cultures for 72 h. As a consequence, it can be suggested that cellular Fe utilisation, and not Fe uptake, might be the main metabolic pathway impaired by Al.
有人提出铝（Al）对红细胞生成有有害影响。然而，其作用机制仍不确定。目前的工作旨在确定铝如何影响人红白血病细胞系K562中的铁（Fe）代谢。这些表达表面转铁蛋白受体（TfRs）的细胞，在含有脱铁转铁蛋白（apoTf）的培养基中培养72小时，通过血红素或羟基脲诱导其向红系分化。在柠檬酸铝存在的情况下，当用血红素诱导培养时，联苯胺阳性细胞数量减少了18%，当用羟基脲作为诱导剂时减少了30%。细胞活力始终未受影响。通过竞争试验发现，125I-Tf-Fe2的表面结合与Tf-Al2浓度（从2.5到10 nM）呈负相关（p < 0.05）。计算了TfRs与配体Tf-Fe2和Tf-Al2之间结合反应的解离常数（Kd）。相同数量级的Kd值表明TfR对Tf-Fe2（Kd = 1.75 x 10(-9) M）和Tf-Al2（Kd = 1.37 x 10(-9) M）具有相似的亲和力。通过动力学125I-Tf-Fe2结合试验测量，在铝存在下培养的诱导细胞中表面TfRs的数量更高。然而，尽管观察到细胞血红蛋白化受到抑制，但72小时内59Fe掺入值与对照培养物中测量的值没有差异。因此，可以认为细胞铁利用而非铁摄取可能是铝损害的主要代谢途径。
