Metabolite Identification of a Radiotracer by Electrochemistry Coupled to Liquid Chromatography with Mass Spectrometric and Radioactivity Detection
Metabolite Identification of a Radiotracer by Electrochemistry Coupled to Liquid Chromatography with Mass Spectrometric and Radioactivity Detection
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DOI：
10.1021/ac2002092
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发表时间：
2011-07-01
影响因子：
7.4
通讯作者：
Karst, Uwe
中科院分区：
文献类型：
--
作者：
Baumann, Anne;Faust, Andreas;Karst, Uwe
放射性配体特异性结合受体或酶（靶标），能够通过正电子发射断层扫描（PET）对靶标表达进行分子成像。一种非常有前景的PET示踪剂是（S）-1-（4-（2-[F-18]-氟乙氧基）苄基）-5-[1-（2-甲氧基甲基吡咯烷基）磺酰基]靛红（靛红），其是一种半胱天冬酶-3抑制剂，已在明斯特大学医院开发用于成像细胞死亡（凋亡）。这种新型示踪剂从临床前评价到临床检查的转化需要生物分布研究，其表征化合物的药效学和代谢命运。该信息用于进一步优化放射性配体，并解释在体内注射放射性配体时来自组织的放射性信号的特异性。放射性配体代谢的分析受到通常注射的化合物的低量（每次注射的纳/皮摩尔量）的阻碍。在本研究中，电化学（EC）的应用，以阐明氧化代谢途径的放射性示踪剂。以往的研究表明，EC可以作为一种补充工具，在药物代谢研究的传统体外方法。因此，潜在的氧化代谢产物的靛红的EC耦合电喷雾电离质谱法（EC/ESI-MS）确定。此外，使用EC/液相色谱（LC）和ESI-离子阱MSn，进行氧化产物的结构解析。与EC相比，使用大鼠肝微粒体进行体外代谢研究。最后，开发的LC/ESI-MS方法应用于测定体液和细胞提取物中的代谢物与非放射性（F-19）和放射性靛红（F-18）的体内研究。基于放射性配体电化学产生的氧化产物，成功鉴定了体内发生的主要放射性代谢产物。
Radioligands, which specifically bind to a receptor or enzyme (target), enable molecular imaging of the target expression by positron emission tomography (PET). One very promising PET tracer is (S)-1-(4-(2-[F-18]-fluoroethoxy)benzyl)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin (isatin), a caspase-3 inhibitor, which has been developed at the University Hospital of Munster to image cell death (apoptosis). The translation of this novel tracer from preclinical evaluation to clinical examinations requires biodistribution studies, which characterize the pharmakodynamics and metabolic fate of the compound. This information is used to further optimize the radioligands and to interpret radioactive signals from tissues upon injection of the radioligand in vivo with respect to their specificity. The analysis of the metabolism of radioligands is hampered by the low amount of the compound being typically injected (nano/picomolar amount per injection). In the present study, electrochemistry (EC) is applied to elucidate the oxidative metabolism pathway of the radiotracer. Previous studies have demonstrated that EC can be utilized as a complementary tool to conventional in vitro approaches in drug metabolism studies. Thereby, potential oxidative metabolites of the isatin are determined by EC coupled to electrospray ionization mass spectrometry (EC/ESI-MS). Moreover, using EC/liquid chromatography (LC) and ESI-ion trap MSn, structural elucidation of the oxidation products is performed. Comparatively to EC, in vitro metabolism studies with rat liver microsomes are conducted. Finally, the developed LC/ESI-MS method is applied to determine metabolites in body fluids and cell extracts from in vivo studies with the nonradioactive (F-19) and radioactive isatin (F-18). On the basis of the electrochemically generated oxidation products of the radioligand, the major radioactive metabolite occurring in vivo was successfully identified.