Cordier-Bussat M, Bernard C, Haouche S, Roche C, Abello J, Chayvialle J A, Cuber J C
INSERM U-45, Hopital Edouard Herriot, Lyon, France.
Endocrinology. 1997 Mar;138(3):1137-44. doi: 10.1210/endo.138.3.5023.
In rats, protein hydrolysates (peptones) stimulate cholecystokinin (CCK) release both in vivo and in a model of isolated vascularly perfused duodeno-jejunum. However, the mechanisms involved in peptone-induced stimulation of CCK cells are not well understood. In particular, the possibility that peptones may directly interact with CCK-producing cells to stimulate CCK release and gene transcription has not yet been examined. To test this hypothesis, we used the enteroendocrine cell line STC-1. Incubation of STC-1 cells for 2 h with albumin egg hydrolysate over the concentration range 0.01-1% (wt/ vol) caused a dose-dependent release of CCK, with a maximal increase at 1420% of the control value. In contrast, BSA (1%, wt/vol) or a mixture of amino acids (1%, wt/vol) induced a modest rise in CCK secretion. A dose-dependent, hydrolysate-specific, increase in the CCK steady state RNA level was also observed. It was detectable by 2-4 h of peptone treatment and sustained until 24-48 h. Peptones did not increase the CCK RNA level in the colonic CCK-producing cell line GLUTag or in nonintestinal CCK-expressing cell lines, namely the pancreatic cell line RINm5F and the medullar thyroid carcinoma cell line CA77. The peptone-induced increase in the CCK RNA level resulted from enhanced gene transcription, because labeled CCK transcripts from nuclear run-on incubations increased 3-fold when cells were incubated with peptones, whereas the level of beta-actin transcripts was not modified. Finally, peptones dose-dependently stimulated the transcriptional activity of an 800-bp fragment of CCK gene promoter transfected in STC-1 cells. These studies indicate that peptones specifically stimulate CCK secretion and gene transcription in the intestinal cell line STC-1, and that cis-acting elements conferring peptone inducibility are located in the first 800 bp of the 5'-flanking region of the CCK gene.
在大鼠中，蛋白质水解产物（蛋白胨）在体内以及在离体血管灌注十二指肠 - 空肠模型中均可刺激胆囊收缩素（CCK）释放。然而，蛋白胨诱导CCK细胞受刺激的机制尚未完全明确。特别是，蛋白胨可能直接与产生CCK的细胞相互作用以刺激CCK释放和基因转录的可能性尚未得到研究。为了验证这一假设，我们使用了肠内分泌细胞系STC - 1。用浓度范围为0.01 - 1%（重量/体积）的白蛋白卵水解产物孵育STC - 1细胞2小时，可导致CCK呈剂量依赖性释放，最大增加至对照值的1420%。相比之下，牛血清白蛋白（1%，重量/体积）或氨基酸混合物（1%，重量/体积）诱导CCK分泌有适度增加。还观察到CCK稳态RNA水平呈剂量依赖性、水解产物特异性增加。蛋白胨处理2 - 4小时即可检测到，并且持续至24 - 48小时。蛋白胨不会增加结肠中产生CCK的细胞系GLUTag或非肠道表达CCK的细胞系（即胰腺细胞系RINm5F和甲状腺髓样癌细胞系CA77）中的CCK RNA水平。蛋白胨诱导的CCK RNA水平增加是由于基因转录增强，因为当细胞与蛋白胨一起孵育时，来自核延伸转录实验的标记CCK转录本增加了3倍，而β - 肌动蛋白转录本的水平未改变。最后，蛋白胨剂量依赖性地刺激了转染到STC - 1细胞中的CCK基因启动子800 bp片段的转录活性。这些研究表明，蛋白胨特异性刺激肠细胞系STC - 1中的CCK分泌和基因转录，并且赋予蛋白胨诱导性的顺式作用元件位于CCK基因5'侧翼区域的前800 bp中。
