Mardirossian G, Wu C, Rusckowski M, Hnatowich D J
Department of Nuclear Medicine, University of Massachusetts Medical Center, Worcester 01655.
Nucl Med Commun. 1992 Jul;13(7):503-12. doi: 10.1097/00006231-199207000-00005.
The anti-CEA FO23C5 F(ab')2 antibody was directly radiolabelled with 99mTcm by two methods (stannous ion and mercaptoethanol reduction) and compared in vitro and in vivo for label stability. By both methods, reduction of the F(ab')2 fragment produced primarily Fab' fragments. By both methods, the label was stable to 99Tcm-pertechnetate formation in vitro. Analysis by high performance liquid chromatography (HPLC) of serum, urine, kidney and liver homogenates from mice injected with 99Tcm-antibodies by both methods consistently showed a prominent radiolabelled peak with an estimated molecular weight of about 300 daltons. An identical peak was observed in the analysis of patient samples in a related investigation from this laboratory. Cysteine was radiolabelled with reduced 99Tcm and analysed by HPLC and thin layer chromatography (TLC); one of the 99Tcm-cysteine species so produced showed the same chromatographic behaviour as that of the 300 dalton species. In conclusion, the FO23C5 and other antibodies are stably labelled with 99Tcm via either stannous ion or mercaptoethanol reduction. In mice and in patients, the labelled proteins are either catabolized or, more likely, the 99Tcm label is transchelated such that the label is present on several low molecular weight species, the most prominent of which is postulated to be 99Tcm-cysteine.
抗癌胚抗原（CEA）的FO23C5 F(ab')2抗体通过两种方法（亚锡离子和巯基乙醇还原法）直接用99mTc进行放射性标记，并在体外和体内对标记稳定性进行了比较。通过这两种方法，F(ab')2片段的还原主要产生Fab'片段。通过这两种方法，标记在体外对99Tcm-高锝酸盐的形成是稳定的。对通过这两种方法注射99Tcm-抗体的小鼠的血清、尿液、肾脏和肝脏匀浆进行高效液相色谱（HPLC）分析，始终显示出一个突出的放射性标记峰，估计分子量约为300道尔顿。在本实验室的一项相关研究中，对患者样本的分析中也观察到了相同的峰。用还原后的99Tcm对半胱氨酸进行放射性标记，并通过HPLC和薄层色谱（TLC）进行分析；如此产生的一种99Tcm-半胱氨酸物种显示出与300道尔顿物种相同的色谱行为。总之，FO23C5和其他抗体通过亚锡离子或巯基乙醇还原法用99Tcm进行稳定标记。在小鼠和患者体内，标记的蛋白质要么被分解代谢，要么更有可能是99Tcm标记被转螯合，使得标记存在于几种低分子量物种上，其中最突出的据推测是99Tcm-半胱氨酸。
