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目的：建立甘氨酸延伸型胃泌素胞浆膜受体结合试验，并应用该方法检测甘氨酸延伸型胃泌素受体的部分特 性及其在正常结肠和人结直肠肿瘤中的表达。方法：用人结直肠肿瘤细胞株ＤＬＤ－１建立胞浆膜制备方法，１２５Ｉ标记 的甘氨酸延伸型胃泌素进行受体结合试验。结果：胞浆膜受体结合试验的条件为： ５～１０ ｍｇ胞浆膜（离心２５ ０００ ｒ／ ｍｉｎ ４５ ｍｉｎ制备），３７ ℃温育６０ ｍｉｎ。正常Ｓｐｒａｇｕｅ－Ｄａｗｌｅｙ大鼠结肠粘膜和从结肠粘膜制备的胞浆膜有特异结合， 而从完整结肠制备的胞浆膜无特异结合。胞浆膜甘氨酸延伸型胃泌素受体抑制５０％结合的非标记配体浓度（ＩＣ５０）为 ３．６４ μｍｏｌ／Ｌ±１．９３μｍｏｌ／Ｌ；特异性胆囊收缩素（ＣＣＫ）－Ａ受体拮抗剂Ｌ３６４和特异性ＣＣＫＢ受体拮抗剂Ｌ３６５不能 拮抗该受体；非特异性受体拮抗剂氯苯酰色氨酸则能拮抗。结论：甘氨酸延伸型胃泌素受体位于正常大鼠结肠粘 膜、结肠粘膜和结直肠肿瘤细胞膜上，属单结合位点、低亲和力受体，不能被特异性ＣＣＫ－Ａ或ＣＣＫ－Ｂ受体拮抗剂拮 抗，是一种新受体。
OBJECTIVE: To establish a glycine-extended gastrin cytosolic receptor binding assay and use this method to detect partial characteristics of the glycine-extended gastrin receptor and its expression in normal colon and human colorectal tumors. METHODS: The human plasma colorectal cancer cell line DLD-1 was used for the preparation of cytoplasmic membranes and 125I-labeled glycine extended gastrin for receptor binding assays. RESULTS: The conditions for binding of cytosolic membrane receptors were: 5 to 10 mg of cytoplasmic membrane (prepared by centrifugation at 25 000 r/min for 45 min) and incubation at 37 °C for 60 min. Normal Sprague-Dawley rats had specific binding to the cytoplasmic membrane prepared from the mucosa of the colon, whereas the plasma membrane prepared from the intact colon had no specific binding. Plasma membrane glycine-extended gastrin receptor inhibits 50% binding with an unlabeled ligand concentration (IC50) of 3.64 μmol/L ± 1.93 μmol/L; specific cholecystokinin (CCK)-A receptor Antagonist L364 and the specific CCKB receptor antagonist L365 could not antagonize this receptor; the nonspecific receptor antagonist chlorobenzoyl tryptophan could antagonize it. Conclusion: The glycine-extended gastrin receptor is located in the colon mucosa of normal rats, colon mucosa, and colorectal tumor cell membranes. It is a single-binding site and low-affinity receptor and cannot be specific for CCK-A or CCK-B receptors. Antagonist antagonism, is a new receptor.