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目的建立一种125I-substanceP（SP）测定脑内SP受体的方法。方法15只家兔断头后取下丘脑和腹侧延髓，低温（0－4℃）离心法制备突触小体，考马斯亮兰蛋白测定剂检测匀浆受体蛋白含量，不同浓度的125I-SP与受体制品孵育后，离心法终止配体受体结合反应，最后以γ闪烁计数仪测出总结合量和非特异结合量，计算特异结合值，根据Scatchard公式求出SP受体总数Bmax，和平衡解离常数Kd。结果1．下丘脑：Bmax107．8±5．2foml／mg受体蛋白，Kd=0.0149±0．004nM；延髓：Bmax33．90±2．22foml／mg受体蛋白；Kd＝0．0141±0．006nM。2．125I－SP终浓度为1．56×10-7M时特异结合与非特异结合比值高于终浓度为3．12×10-7M（P＜0．05）；结论本方法简便，快速，特异结合信号较强，费用低；125I-SP的用量是影响其与SP受体特异结合的重要因素。
Objective To establish a 125I-substanceP (SP) method for the determination of SP receptors in the brain. Methods Fifteen rabbits were sacrificed by decapitation and thalamic medulla oblongata. Synaptosomes were prepared by low temperature (0-4 ° C) centrifugation. Coomassie brilliant blue protein was used to measure the protein content of homogenate receptor. Different concentrations of 125I- SP incubated with the receptor products, the termination of ligand receptor binding reaction by centrifugation, and finally the total binding amount and non-specific binding was measured by γ scintillation counter to calculate the specific binding value, according to Scatchard formula SP receptor total number Bmax , And equilibrium dissociation constant Kd. Results 1. Hypothalamus: Bmax 107.8 ± 5.2 foml / mg receptor protein, Kd = 0.0149 ± 0.004 nM; medulla oblongata: Bmax 33.90 ± 2.22 foml / mg receptor protein; Kd = 0.0141 ± 0.006 nM. The specific binding to nonspecific binding ratio of 2.125I-SP was 1.56 × 10-7M higher than the final concentration of 3.12 × 10-7M (P <0.05) .Conclusion The method is simple, rapid, The specific binding signal is strong and the cost is low. The dosage of 125I-SP is an important factor affecting its specific binding to SP receptors.