纤维蛋白显像剂131I-YSSCREKA肽的制备及对早期血栓定位的研究

合成了一种可特异性结合纤维蛋白-纤维连接蛋白的早期血栓显像剂¹³¹I-YSSCREKA肽（酪氨酸-（D）丝氨酸-（D）丝氨酸-半胱氨酸-精氨酸-谷氨酸-赖氨酸-丙氨酸），对其标记、SPECT显像及初步生物学性能进行研究。结果表明：YSSCREKA八肽在室温下通过氯胺-T法反应5 min的标记率为(77.2±1.1)%（n=3），放射化学纯度为(90.0±3.1)%（n=3），体外稳定性较好。新西兰家兔SPECT显像显示在¹³¹I-YSSCREKA肽注射后20 h血栓能较清晰地显像，血栓/血放射性比值为1.36。SD大鼠生物分布实验显示：20 h ¹³¹I-YSSCREKA肽在血栓中的摄取率为(0.19±0.06)ID%/g（n=5），血栓/肌肉及血栓/血放射性比值分别为3.80和1.90。¹³¹I-YSSCREKA肽有可能作为早期血栓的显像剂，但其在血栓中的摄取率有待于进一步提高。

Synthesis of Fibrin-Binding Peptide 131 I-YSSCREKA for Targeting Early Thrombosis

To develop the radiotracer for imaging vein thrombosis, the ¹³¹I labeled octapeptide containing CREKA(Cys-Arg-Glu-Lys-Ala) sequence had been proved to bind to fibrin-fibronectin complexes in clotted plasma and was injected into animals models to investigate the targeting effect on early thrombosis. The octapeptide YSSCREKA(Tyr-(D)Ser-(D)Ser-Cys-Arg-Glu-Lys-Ala) was constructed and labeled with ¹³¹I by Ch-T method. The ¹³¹I radiolabeling yield and radiochemical purity are (77.2±1.1)% and (90.0±3.1)%（n=3） respectively. ¹³¹I-YSSCREKA performs high stability in vitro at room temperature within 72 h. The fresh vein thrombus is clearly visible at 20 h on inferior vena cava of rabbits. The count ratio of thrombus/blood by region of interest(ROI) method is 1.36. The thrombus uptake of radiolabeled peptide at 20 h post-injection is (0.19±0.06)ID%/g（n=5）. The count ratios of thrombus/muscle and thrombus/blood are 3.80 and 1.90, respectively. ¹³¹I-YSSCREKA is a promising tracer for early thrombosis and is worthy to be further studied to improve the thrombus uptake.