Kriegerbecková K, Döpper L, Scheiber B, Kovár J, Goldenberg H
Institut für Medizinische Chemie, Universität Wien, Austria.
Eur J Clin Chem Clin Biochem. 1995 Nov;33(11):791-7. doi: 10.1515/cclm.1995.33.11.791.
HeLa cells cultured in defined serum-free media supplied with iron wither in the form of diferric transferrin (transferrin-dependent cells), ferric citrate at 500 micromol/l (high-iron dependent cells) or ferric citrate at 5 micromol/l (low-iron dependent cells) accumulate iron from ferric citrate in different ways. The uptake rate in transferrin-dependent cells is always much lower in the other two lines. In all three, the uptake rate rises almost linearly with the concentration of iron up to 10 micromol/l. In high-iron dependent cells, the uptake of radiolabelled iron is suppressed by a 100-fold excess of the iron complex, whereas this same excess stimulates iron uptake in the other two lines. The same concentrations of pure citrate completely inhibit iron uptake by all three types of cell. Only high-iron dependent cells take up citrate at measurable and reproducible rates. These rates are independent on the presence of iron, and the uptake is inhibited by an unlabelled surplus. The pH-dependence of iron uptake in high-iron dependent cells is also different from that of the other cells. Low-iron dependent cells transferred to medium containing 500 micromol/l iron show increased uptake rates within 3 to 7 h, and after overnight maintenance in this medium they acquire the uptake characteristics of high-iron dependent cells. The special characteristics of iron uptake by high-iron dependent cells are paralleled by low binding activity of iron-regulatory protein to iron-responsive elements of RNA. We conclude that low-iron dependent cells maintain their iron supply from the culture medium by unspecific uptake of oligomeric complexes, while cells in media with a high content of low-molecular weight iron induce a specific uptake system which might have a protective function.
在添加了铁的限定无血清培养基中培养的HeLa细胞，铁以二价铁转铁蛋白（转铁蛋白依赖性细胞）、500微摩尔/升柠檬酸铁（高铁依赖性细胞）或5微摩尔/升柠檬酸铁（低铁依赖性细胞）的形式存在，它们以不同方式从柠檬酸铁中积累铁。转铁蛋白依赖性细胞的摄取率在另外两种细胞系中总是低得多。在所有三种细胞中，摄取率几乎随铁浓度线性上升，直至10微摩尔/升。在高铁依赖性细胞中，放射性标记铁的摄取受到铁复合物100倍过量的抑制，而同样的过量在另外两种细胞系中则刺激铁摄取。相同浓度的纯柠檬酸盐完全抑制所有三种细胞类型的铁摄取。只有高铁依赖性细胞以可测量且可重复的速率摄取柠檬酸盐。这些速率与铁的存在无关，且摄取受到未标记过量物的抑制。高铁依赖性细胞中铁摄取的pH依赖性也与其他细胞不同。转移到含有500微摩尔/升铁的培养基中的低铁依赖性细胞在3至7小时内摄取率增加，并且在该培养基中过夜培养后，它们获得了高铁依赖性细胞的摄取特征。高铁依赖性细胞铁摄取的特殊特征与铁调节蛋白对RNA铁反应元件的低结合活性平行。我们得出结论，低铁依赖性细胞通过非特异性摄取寡聚复合物来维持其从培养基中的铁供应，而在低分子量铁含量高的培养基中的细胞诱导一种可能具有保护功能的特异性摄取系统。
