【摘要】 目的探讨（99）^Tc^m 标记突触结合蛋白Ⅰ的 C2A 片段-谷胱甘肽转移酶复合物（FM2）在心肌细胞凋亡显像中的应用价值。方法通过基因工程合成 FM2,以2-亚氨基噻吩盐酸盐（IT）修饰,经葡庚糖酸钠（GH）转换标记制备（99）^Tc^m-FM2。（99）^Tc^m-FM2经纯化后,纸层析法测定放化纯。破碎红细胞膜磷脂结合实验检测（99）^Tc^m-FM2在 Ca²⁺介导下与凋亡细胞表面磷脂结合的能力。以6头小型猪制备心肌凋亡模型,通过心导管将球囊送入并充气阻塞冠状动脉主要分支远端（左前降支、左回旋支或右冠状动脉）,20～30 min 后,撤除球囊,造成缺血再灌注损伤,引发急性心肌梗死。注射（99）^Tc^m-FM2后3 h,进行 CT 定位和 SPECT 显像,计算心肌异常高放射性区/本底（T/B）比值。处死动物,体外测定凋亡心肌与正常心肌的单位质量放射性比值。用流式细胞分析和电镜检查验证显像结果。结果 （99）^Tc^m-FM2稳定,放化纯>95%。FM2经（99）^Tc^m 标记后仍保持 Ca²⁺介导的与膜磷脂特异结合的能力。活体显像:（99）^Tc^m-FM2注射后3 h,凋亡心肌清晰显影,T/B 比值为3.36±0.74。体外测定:缺血再灌注损伤心肌与正常心肌的单位质量放射性比值为11.68±4.02。流式细胞分析和电镜检查均证实心肌高放射性区凋亡心肌组织形成。结论 （99）^Tc^m-FM2在活体内与凋亡心肌组织特异结合,对无创性检测心肌细胞凋亡有潜在应用价值。更多还原

【Abstract】 Objective To evaluate the value of ⁹⁹Tc^m-C2A domain of synaptotagmin l-glutathi- one-S-transferase fusion protein（FM2）for the non-invasive assessment of myocardial apoptosis using SPECT.Methods Recombinant C2A domain of synaptotagmin Ⅰ was overexpressed in E.Coli,and puri- fied as glutathione-S-transferase,FM2 was produced through this process.FM2 was thiolated with 2-imino- thiolane（2-IT）and labeled with ⁹⁹Tc^m.Radiochemical purity was determined with thin layer chromatogra- phy.To ensure that the binding activity of ⁹⁹Tc^m-FM2 and Ca²⁺-dependent phosphatidylserine（PS）was re- tained.⁹⁹Tc^m-FM2 was tested by using lyses blood cell membranes in both presence and absence of Ca²⁺. The radintracer was tested with ischemia-reperfusion models in 6 pigs.Briefly,occlusion of the left descend- ing coronary artery or circumflex branch or right coronary artery of adult pigs was induced by balloon angio- plasty for 20～30 min,then followed by reperfusion.⁹⁹Tc^m-FM2 was intravenously injected and SPECT ima- ges were acquired at 3 h post-injection.Results ⁹⁹Tc^m-FM2 had good radiochemical purity（>95%）; and the binding activity of ⁹⁹Tc^m-FM2 and Ca²⁺-dependent PS was well preserved.There was focal uptake of radioactivity at the experimental infarct areas,with target/background（T/B）ratio being 3.36±0.74 in pigs at 3 h post-injection of the radiotracer using SPECT,while T/B ratio was 11.68±4.02 in direct count- ing of the infarct tissue and normal myocardium.Myocardial apoptosis in infarct areas was confirmed by flow cytometry and electron microscopy.Conclusions ⁹⁹Tc^m-FM2 binds to apoptotic cells by recognizing ex- posed PS as a molecular marker.It should be a potential radiotracer for imaging of myocardial apoptosis.更多还原