生长抑素-葡聚糖的99Tcm标记及体外结合分析

采用还原氨化方法，将天然生长抑素（SMS）与葡聚糖(Dx20)偶联，并以125I－奥曲肽（125I-Tyr3-Octreotide)为放射配基，进行受体竞争结合实验，测定了SMS-Dx50的IC50；以SnCl2为还原剂对SMS-Dx50进行99Tcm标记，并进行99Tcm- SMS-Dx50受体结合分析，考察其对生长抑素受体的亲合能力。结果表明：SMS-Dx50保持了对SMS 2型受体的高亲和力；其IC50与奥曲肽的IC50（0.79 nmol/L）相近,为5.95 nmol/L；99Tcm- SMS-Dx50标记率>85％, 经PD-10柱分离纯化，其放化纯度>98%；99Tcm- SMS-Dx50对生长抑素2型受体特异性结合为25%～40％，保持了较高的亲和力；SMS-Dx50适合于99Tcm标记，可用于生长抑素受体阳性肿瘤诊断的进一步研究

99Tcm Labeling and in Vitro Binding of Dextran-somatostatin Conjugate

Natural somatostatin and dextran-20 are used to synthesis somatostatin-dextran(SMS-Dx~(20)).The in vitro somatostatin receptor competition binding study of somatostatin-dextran is carried out by using rat brain cortex membranes(express somatostatin receptor type 2) and ~(125)I-Tyr~3-Octreotide as a radioligand.The somatostatin-dextran conjugate is then labelled with ~(99)Tc~m using SnCl_2 as reduce agent and tested for its in vitro binding properties.The somatostatin-dextran conjugate shows high somatostatin receptor binding affinity,i.e.in the same IC_(50) value as the reference ligand Octreotide(IC_(50)~ 5.95 nmol/L).The labeling efficiency is more than 85%.The specific binding of ~(99)Tc~m labeled somatostatin-dextran conjugate is 25%~40%.The somatostatin-dextran conjugate is worthy of further investigation for ~(99)Tc~m radiolabeling with diagnostic posibilities for somatostatin receptor positive tumors.