Nakamura K, Kawaguchi H, Shimizu K, Orii H
Eur J Nucl Med. 1984;9(5):237-40. doi: 10.1007/BF00448546.
The binding of gallium 67 or iron 59 to ferritin in vitro was investigated using equilibrium dialysis. Gallium 67 did not bind to apo-ferritin until the protein was transformed into ferritin in the presence of iron citrate. Apotransferrin inhibited the binding of 67Ga to ferritin, especially in the presence of sodium bicarbonate and citrate, thus indicating that 67Ga has not gained access to ferritin from its complex with transferrin. Similar inhibition was observed for ferritin-59Fe. The release of 59Fe from its transferrin complex was enhanced by ATP, citrate, or ascorbic acid, while these reagents did not stimulate the dissociation of 67Ga from its transferrin complex. On the other hand, 67Ga injected intravenously in vivo was not found in the ferritin fractions of rat liver, kidney, and tumor. The difference between experimental results in vivo and in vitro supports the hypothesis that 67Ga in the cytoplasm is not labile enough to be bound to ferritin. We have indicated a significant role of ferritin in distinguishing between 67Ga and 59Fe in the cell, and provided some clues to interpret the chemical forms of 67Ga in the cytoplasm.
利用平衡透析法研究了镓67或铁59在体外与铁蛋白的结合情况。在柠檬酸铁存在下蛋白质转化为铁蛋白之前，镓67不与脱铁铁蛋白结合。运铁蛋白原抑制67Ga与铁蛋白的结合，尤其是在存在碳酸氢钠和柠檬酸盐的情况下，这表明67Ga无法从其与运铁蛋白的复合物中进入铁蛋白。对于铁蛋白-59Fe也观察到类似的抑制作用。ATP、柠檬酸盐或抗坏血酸可增强59Fe从其运铁蛋白复合物中的释放，而这些试剂不会刺激67Ga从其运铁蛋白复合物中解离。另一方面，静脉内注射到体内的67Ga在大鼠肝脏、肾脏和肿瘤的铁蛋白组分中未被发现。体内和体外实验结果的差异支持了细胞质中的67Ga不够不稳定而无法与铁蛋白结合的假说。我们指出了铁蛋白在细胞中区分67Ga和59Fe方面的重要作用，并提供了一些线索来解释细胞质中67Ga的化学形式。
