Scheiber B, Goldenberg H
Institut für Medizinische Chemie, Universität Wien, Vienna, Austria.
Arch Biochem Biophys. 1996 Feb 15;326(2):185-92. doi: 10.1006/abbi.1996.0064.
We studied uptake of iron from Fe(III)-diethylenetriamine pentaacetate (DTPA) in isolated rat hepatocytes. This uptake is specific with an affinity of 600 nM and shows an optimum pH of 6. The specificity is indicated by inhibition by ferric citrate and diferric transferrin. Iron uptake from Fe(III)-DTPA is completely inhibited by trypsinization of the cell surface, by strong impermeant ferric chelators (DTPA, apo-transferrin, polymer-conjugated desferrioxamine), both hexacyanoferrates, copper and zinc, and partly by dipyridyl, manganese, cobalt, N-ethylmaleimide, and citrate. The lysosomotropic agent chloroquin inhibits weakly; proton pump inhibitors are without effect. Ascorbate and Tiron both effectively stimulate the uptake and also mobilize iron from DTPA in vitro. Approximately 75% of the freshly acquired intracellular iron is found in ferritin even after uptake at lowered temperature (16 degrees C). We conclude that a rate-limiting mobilization of iron from the DTPA chelate by a cell-surface activity is required before iron can actually enter the cell. This can be enhanced by mediators of iron release, but does not seem to require reduction of iron. The use of DTPA as chelator offers the possibility of studying this putative activity because the Fe(III)-DTPA chelate is stable in the presence of transferrin or desferroxamine, in contrast to ferric citrate or Fe(NTA)2.
我们研究了铁从三价铁-二乙烯三胺五乙酸（DTPA）进入分离的大鼠肝细胞的摄取情况。这种摄取具有特异性，亲和力为600 nM，最佳pH值为6。柠檬酸铁和二价铁转铁蛋白可抑制摄取，表明其具有特异性。细胞表面经胰蛋白酶处理、强非渗透性铁螯合剂（DTPA、脱铁转铁蛋白、聚合物共轭去铁胺）、两种六氰合铁酸盐、铜和锌均可完全抑制铁从Fe(III)-DTPA的摄取，联吡啶、锰、钴、N-乙基马来酰胺和柠檬酸盐可部分抑制。溶酶体促渗剂氯喹抑制作用较弱；质子泵抑制剂无效。抗坏血酸盐和钛铁试剂在体外均能有效刺激摄取，并能从DTPA中动员铁。即使在低温（16℃）摄取后，新摄取的细胞内铁中约75%存在于铁蛋白中。我们得出结论，在铁实际进入细胞之前，需要通过细胞表面活性将铁从DTPA螯合物中进行限速动员。这可通过铁释放介质增强，但似乎不需要铁的还原。使用DTPA作为螯合剂提供了研究这种假定活性的可能性，因为与柠檬酸铁或Fe(NTA)2相比，Fe(III)-DTPA螯合物在转铁蛋白或去铁胺存在下是稳定的。
