Jin Y, Baquet A, Florence A, Crichton R R, Schneider Y J
Université Catholique de Louvain, Unité de Biochimie, Louvain-La- Neuve, Belgium.
Biochem Pharmacol. 1989 Oct 1;38(19):3233-40. doi: 10.1016/0006-2952(89)90619-9.
3H-Desferrithiocin (DFT) has been synthesized from desmethyl desferrithiocin. The uptake and release of this 3H siderophore and of its iron complex have been studied in cultured rat hepatocytes and systematically compared to 14C desferrioxamine B (DFO). At 37 degrees, the uptake of both chelators is strictly proportional to the extracellular concentration and no toxicity is observed up to, at least, 1 mM. Uptake of 3H DFT is rapid and reaches a plateau after ca. 1 hr. The accumulation of 3H DFT attains a maximum three times that of 14C DFO and the plateau is reached much more rapidly. Upon reincubation in a drug-free medium of cells that had accumulated 3H DFT, most of the 3H label is rapidly released in the culture medium. These kinetic parameters suggest that the accumulation of these two chelators results from their diffusion across cellular membranes, as a function of the gradient of concentration between the cellular compartment and the extracellular medium. Differential centrifugation of homogenates from hepatocytes incubated with 3H DFT shows that the bulk of cell associated 3H-label (82%) is found in the cytosol, whereas a small proportion (14.5%) is present in the particulate fraction. Isopycnic centrifugation on sucrose gradients suggests that 3H-label associated with the particulate fraction is localized within mitochondria. In contrast, 14C DFO distributes in almost equal proportions between cytosol and the particulate fraction (MLP). At least part of the 14C-label in MLP is associated with lysosomes. Rat hepatocytes cultivated for long term in synthetic culture medium have been used to study iron mobilization by chelators from 59Fe loaded cells. DFT mobilizes iron more rapidly than DFO. This effect is also observed in vitro with ferritin, where, in addition, DFT is much more efficient than DFO to mobilize iron at acidic pH. These results strongly suggest that different iron mobilization from cultured hepatocytes results from differences in the cellular pharmacology of these two chelators and, in particular, in their rate of uptake, cellular accumulation levels and subcellular localizations. DFT could mobilize iron from cytosol and, possibly, to a small extent from mitochondria, whereas DFO would do so from cytosol and lysosomes.
3H-去铁硫菌素（DFT）由去甲基去铁硫菌素合成。在培养的大鼠肝细胞中研究了这种3H铁载体及其铁络合物的摄取和释放，并与14C去铁胺B（DFO）进行了系统比较。在37℃时，两种螯合剂的摄取与细胞外浓度严格成正比，至少在1 mM时未观察到毒性。3H DFT的摄取迅速，约1小时后达到平台期。3H DFT的积累量达到14C DFO的三倍最大值，且更快达到平台期。在积累了3H DFT的细胞的无药物培养基中再培养时，大部分3H标记物迅速释放到培养基中。这些动力学参数表明，这两种螯合剂的积累是由于它们跨细胞膜的扩散，这是细胞内区室和细胞外介质之间浓度梯度的函数。用3H DFT孵育的肝细胞匀浆的差速离心显示，大部分与细胞相关的3H标记（82%）存在于胞质溶胶中，而一小部分（14.5%）存在于颗粒部分。在蔗糖梯度上的等密度离心表明，与颗粒部分相关的3H标记定位于线粒体内。相比之下，14C DFO在胞质溶胶和颗粒部分（MLP）中几乎以相等的比例分布。MLP中至少部分14C标记与溶酶体相关。长期在合成培养基中培养的大鼠肝细胞已被用于研究螯合剂从59Fe负载细胞中动员铁的情况。DFT比DFO更快地动员铁。在体外对铁蛋白也观察到这种效果，此外，在酸性pH下，DFT比DFO更有效地动员铁。这些结果强烈表明，从培养的肝细胞中不同的铁动员是由于这两种螯合剂的细胞药理学差异，特别是它们的摄取速率、细胞积累水平和亚细胞定位。DFT可以从胞质溶胶中动员铁，可能在较小程度上也可以从线粒体中动员铁，而DFO则可以从胞质溶胶和溶酶体中动员铁。
