Monstein H J, Nylander A G, Salehi A, Chen D, Lundquist I, Håkanson R
Dept. of Clinical Microbiology, University Hospital, Linköping, Sweden.
Scand J Gastroenterol. 1996 Apr;31(4):383-90. doi: 10.3109/00365529609006415.
Gastrin and cholecystokinin (CCK) are thought to exert trophic effects on the gastrointestinal tract and pancreas. Two types of receptors have been cloned, CCK-A and CCK-B/ gastrin. We have examined the occurrence of CCK-A and CCK-B receptor mRNA in the brain, digestive tract, pancreas, and kidney of the rat and man by Northern blot and reverse transcribed polymerase chain reaction (RT-PCR).
Total RNA was isolated from rat tissues and reverse transcribed into cDNA. cDNA from brain, kidney, and pancreas of the rat and man and from human whole stomach were commercially available. Northern blot and a PCR technique based on Taq polymerase-antibody interaction and using CCK-A and CCK-B receptor-specific primers, followed by Southern blot analysis, were the methods used.
By means of Northern blots, CCK-A receptor mRNA was detected in rat fundus mucosa and pancreas but not in the remaining GI tract or brain. By means of RT-PCR, CCK-A receptor mRNA was demonstrated in the brain and the mucosa of the fundus, antrum, duodenum, and colon, kidney, pancreas and pancreatic islets. CCK-B receptor mRNA was detected by Northern blot analysis in the brain and the fundus mucosa but not in the rest of the digestive tract and not in the pancreas, pancreatic islets, or kidney. By RT-PCR, expression of CCK-B receptor mRNA could also be detected in antrum mucosa. In man, CCK-A receptor mRNA was detected in the brain, stomach, pancreas, and kidney, whereas CCK-B receptor mRNA was found in the brain, stomach, and pancreas but not in the kidney. Cloning and DNA-sequence analysis of the PCR-amplified rat and human CCK-A and CCK-B receptor DNA fragments, which cover the protein-encoding regions of the intracellular loop C3, showed complete sequence homology as compared with published rat and human sequences.
It appears unlikely that CCK will have effects in the ileum, at least not effects mediated by CCK-A receptors. It also appears unlikely that physiologic concentrations of gastrin in the circulation will promote growth (or exert other effects) in the pancreas, duodenum, ileum, and colon, since CCK-B receptor mRNA is not expressed or is poorly expressed in these tissues.
胃泌素和胆囊收缩素（CCK）被认为对胃肠道和胰腺具有营养作用。已克隆出两种类型的受体，即CCK-A和CCK-B/胃泌素受体。我们通过Northern印迹法和逆转录聚合酶链反应（RT-PCR）检测了大鼠和人类大脑、消化道、胰腺及肾脏中CCK-A和CCK-B受体mRNA的表达情况。
从大鼠组织中提取总RNA并逆转录成cDNA。大鼠和人类大脑、肾脏、胰腺以及人类全胃的cDNA可通过商业途径获得。所采用的方法包括Northern印迹法以及基于Taq聚合酶-抗体相互作用并使用CCK-A和CCK-B受体特异性引物的PCR技术，随后进行Southern印迹分析。
通过Northern印迹法，在大鼠胃底黏膜和胰腺中检测到CCK-A受体mRNA，但在其余胃肠道或大脑中未检测到。通过RT-PCR，在大脑、胃底、胃窦、十二指肠和结肠的黏膜、肾脏、胰腺及胰岛中均证实有CCK-A受体mRNA表达。通过Northern印迹分析在大脑和胃底黏膜中检测到CCK-B受体mRNA，但在消化道其余部分、胰腺、胰岛或肾脏中未检测到。通过RT-PCR，在胃窦黏膜中也可检测到CCK-B受体mRNA的表达。在人类中，在大脑、胃、胰腺和肾脏中检测到CCK-A受体mRNA，而在大脑、胃和胰腺中发现有CCK-B受体mRNA，但在肾脏中未发现。对PCR扩增的大鼠和人类CCK-A和CCK-B受体DNA片段（覆盖细胞内环C3的蛋白质编码区域）进行克隆和DNA序列分析，结果显示与已发表的大鼠和人类序列相比具有完全的序列同源性。
CCK似乎不太可能在回肠发挥作用，至少不是通过CCK-A受体介导的作用。循环中生理浓度的胃泌素似乎也不太可能促进胰腺、十二指肠、回肠和结肠的生长（或发挥其他作用），因为这些组织中未表达或低表达CCK-B受体mRNA。
