Brand S J, Morgan R G
J Physiol. 1981;319:325-43. doi: 10.1113/jphysiol.1981.sp013911.
The distribution, molecular form and release of cholecystokinin (CCK)-like activity in extracts of rat small intestine was studied with an in vitro gall-bladder bio-assay. In contrast to the reported heterogeneity of CCK-like immunoreactivity in the intestine, only a single molecular form of CCK-like activity was detected using the bio-assay. 2. The CCK-like activity eluted from Sephadex G50 with a Kav of 0.69, after the triacontriapeptide of cholecystokinin (CCK33) and before cholecystokinin octapeptide 2500, may represent the 22 amino acid peptide of CCK (CCK22). The bio-assay peak of CCK-like activity had pancreozymin activity and CCK/gastrin C terminal immunoreactivity. The CCK-like activity weas readily extracted from the small intestine at neutral pH, but subsequent treatment with cold 0.5 M-acetic acid extracted further CCK-like activity of the same molecular form as that recovered under neutral conditions. 3. The bio-assay detected no CCK-like activity, nor was pancreozymin-like activity found in fractions corresponding to CCK33 or CCK8 after Sephadex G50 chromatography of rat intestinal extracts. 4. Oral trypsin inhibitor was a potent stimulus for the release of CCK-like activity from the upper small intestine of the rat. After oral trypsin inhibitor release, CCK-like activity was rapidly resynthesized.
采用体外胆囊生物测定法，研究了大鼠小肠提取物中胆囊收缩素（CCK）样活性的分布、分子形式及释放情况。与报道的小肠中CCK样免疫反应性的异质性不同，使用该生物测定法仅检测到单一分子形式的CCK样活性。2. 从Sephadex G50洗脱的CCK样活性，其洗脱体积（Kav）为0.69，在胆囊收缩素三十肽（CCK33）之后、胆囊收缩素八肽2500之前，可能代表CCK的22氨基酸肽（CCK22）。CCK样活性的生物测定峰具有促胰酶素活性和CCK/胃泌素C末端免疫反应性。CCK样活性在中性pH值下很容易从小肠中提取出来，但随后用冷的0.5M乙酸处理会进一步提取出与在中性条件下回收的相同分子形式的CCK样活性。3. 生物测定未检测到CCK样活性，大鼠肠提取物经Sephadex G50层析后，在对应于CCK33或CCK8的组分中也未发现促胰酶素样活性。4. 口服胰蛋白酶抑制剂是大鼠上段小肠释放CCK样活性的有效刺激物。口服胰蛋白酶抑制剂释放后，CCK样活性迅速重新合成。
