Gastrin Receptor mRNA Research Articles

The gastrin/cholecystokinin-B receptor on prostate cells – A novel target for bifunctional prostate cancer imaging

The means of identifying prostate carcinoma and its metastases are limited.The contrast agents used in magnetic resonance imaging clinical diagnostics are not taken up into the tumor cells, but only accumulate in the interstitial space of the highly vasculated tumor.We examined the gastrin/cholecystokinin-B receptor as a possible target for prostate-specific detection using the C-terminal seven amino acid sequence of the gastrin peptide hormone. The correct sequence and a scrambled control sequence were coupled to the fluorescent dye rhodamine and the magnetic resonance imaging contrast agent gadolinium (Gd)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA).Expression analysis of the gastrin receptor mRNA was performed by reverse transcriptase polymerase chain reaction on PC3 prostate carcinoma cells, U373 glioma, U2OS osteosarcoma and Colo205 colon carcinoma cells. After having confirmed elevated expression of gastrin receptor in PC3 cells and very low expression of the receptor in Colo205 cells, these two cell lines were used to create tumor xenografts on nude mice for in vivo experiments.Confocal lasers scanning microscopy and magnetic resonance imaging showed a high specificity of the correct conjugate for the PC3 xenografts. Staining of the PC3 xenografts was much weaker with the scrambled conjugate while the Colo205 xenografts showed no marked staining with any of the conjugates.In vitro experiments comparing the correct and scrambled conjugates on PC3 cells by magnetic resonance relaxometry and fluorescence-activated cell sorting confirmed markedly higher specificity of the correct conjugate.The investigations show that the gastrin receptor is a promising tumor cell surface target for future prostate-cancer-specific imaging applications.

Effect of Aging on Gastrin Receptor Gene Expression in Rat Stomach

Waki, S., Y. Kinoshita, H.-Y. Wang, M. Asahara, Y. Matsushima, M. S. Hassan, A. Okada, T. Maekawa, H. Fukui, C. Kawanami, K. Kishi and T. Chiba. Effect of aging on gastrin receptor gene expression in rat stomach. Peptides 19(2) 225–229, 1998.—Gastrin is a pivotal humoral factor which regulates gastric acid secretion through its receptors. There is no report, however, concerning the age-related changes of gastrin receptor gene expression in the stomach. Northern blot analysis and in situ hybridization were performed to clarify the changes of gastrin receptor expression during the aging. In situ hybridization clarified that gastrin receptor mRNA was expressed mainly in enterochromaffin-like (ECL) cells in adult rat gastric mucosa. With aging, gastrin receptor gene expression in the stomach increased with the concomitant increase in histidine decarboxylase mRNA. Since histidine decarboxylase is a marker of gastric ECL cells, the augmented gastrin receptor mRNA in aged rats may be caused by the increased ECL cells in gastric mucosa during the aging.

Gastrin inhibits secretin-induced ductal secretion by interaction with specific receptors on rat cholangiocytes.

We assessed the effect of gastrin on ductal secretion in normal and bile duct-ligated (BDL) rats. The effect of gastrin on ductal secretion was examined in the presence of proglumide, a specific antagonist for gastrin receptor (GR). We isolated pure cholangiocytes from normal and BDL rats and assessed gastrin effects on secretin receptor (SR) gene expression and intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels. We examined the presence of GR mRNA in cholangiocytes by reverse transcription polymerase chain reaction (RT-PCR). In normal or BDL rats, gastrin produced no changes in spontaneous bile secretion. Simultaneous infusion of gastrin inhibited secretin-induced choleresis and bicarbonate output in BDL rats. In the presence of proglumide gastrin did not inhibit secretin-induced choleresis in BDL rats. Gastrin decreased in cholangiocytes from BDL rats 1) SR gene expression and 2) secretin-induced cAMP levels. With the use of RT-PCR, GR mRNA was detected in cholangiocytes. Similar to what is shown for secretin and somatostatin, we propose that the opposing effects of secretin and gastrin on cholangiocyte secretory activity regulate ductal secretion in rats.

Effects of growth factors and gut hormones on proliferation of primary cultured gastric mucous cells of guinea pig.

Almost completely homogenous gastric mucous epithelial cells of guinea pigs were grown to confluence in the presence of 10% fetal calf serum (FCS). FCS, epidermal growth factor (EGF), and insulin significantly increased 5-bromo-2'-deoxyuridine (BrdU) uptake by the cells and EGF together with insulin increased the cells' [3H] thymidine uptake. Basic fibroblast growth factor (bFGF) enhanced EGF-induced DNA synthesis by the cells, but vasoactive intestinal peptide (VIP), secretin, prostaglandin E2 (PGE2), and dibutyryl cyclic AMP (dbcAMP) neither induced DNA synthesis nor enhanced the effect of EGF on DNA synthesis by the cells. Gastrin, cholecystokinin-octapeptide (CCK8), and carbamylcholine chloride (CCh) also did not enhance the effect of EGF on DNA synthesis. 125I-EGF, 125I-bFGF, and 125I-gastrin binding to the gastric mucous cells revealed the presence of high-affinity receptors for EGF and bFGF, but not for gastrin. Northern blot analysis showed the expression of EGF receptor mRNA, but not gastrin receptor mRNA. These results suggest that EGF, insulin, and bFGF may cooperatively regulate gastric mucous cell growth, but that gastrin and other gastrointestinal hormones do not have a direct stimulatory effect on mucous cell growth in the guinea pig.

Gastrin Receptor Expression during Azaserine-Induced Rat Pancreatic Carcinogenesis

The hormone gastrin is thought to stimulate the growth of certain pancreatic carcinoma cell lines. We have previously detected the presence of the gastrin receptor in rat pancreatic carcinoma cell lines but not in normal rat pancreas. We had not, however, previously demonstrated that gastrin receptor is expressed in pancreatic carcinomas developing in the ratin vivo.Therefore, in the present study, we examined rat pancreatic tissue at various stages in azaserine-induced pancreatic carcinogenesis for gastrin binding and for the presence of gastrin receptor mRNA to determine the temporal expression pattern of the gastrin receptor during thein vivodevelopment of pancreatic cancer. Autoradiography of pancreatic tissue using125I-gastrin-17-I from all azaserine-treated and control animals at 2, 4, 8, and 12 months of age demonstrated no specific gastrin binding. At 18 months of age, normal pancreas, azaserine-induced premalignant pancreatic nodules, and internodular pancreas demonstrated no specific gastrin binding. One of three azaserine-treated animals developed an area of pancreatic acinar cell carcinoma at 18 months of age which exhibited significant specific gastrin binding of 141.8 ± 32.8 fmole/gm of tissue. Southern blot analysis of pancreatic RNA isolated from animals at 12 months of age revealed no gastrin receptor mRNA; however, by 18 months of age, gastrin receptor mRNA was present in all azaserine-treated animals but absent in control animals. In summary, specific gastrin binding is present inin vivoazaserine-induced pancreatic acinar cell carcinoma but absent in normal pancreas and azaserine-induced premalignant pancreatic nodules. Gastrin receptor mRNA is first expressed in azaserine-treated rat pancreas at some point between 12 and 18 months of age. These results demonstrate that expression of gastrin receptor is altered in azaserine-treated rat pancreas and may play a role in the development of pancreatic cancer.

Molecular cloning, developmental expression and pharmacological characterization of the [formula omitted] receptor in the calf pancreas

We have cloned the calf predominant pancreatic cholecystokinin B(CCK B) gastrin receptor cDNA. It encodes a 454 amino acid protein with 90% identity with the CCK B gastrin receptor cloned in other species and tissues. However, the calf pancreatic CCK B gastrin receptor contains a pentapeptide cassette within the third intracellular loop which is absent in the cloned human brain and stomach receptor. Quantification of the CCK B gastrin receptor mRNA levels by reverse transcription polymerase chain reaction demonstrated the same level of transcripts at birth, +7 and +28 days. On the other hand, binding study with pancreatic membranes showing a dramatic increase (600-fold) in the number of CCK B gastrin receptor sites between at birth and +28 days indicates that the development of the calf pancreatic CCK B gastrin receptor occurs during the first 4 weeks of post-natal life. COS monkey cells (COS-7 cells) transiently transfected by the cloned cDNA exhibit binding of 125I-Bolton-Hunter-[Thr 28,Ahx 31]CCK-(25–33) and 125I-Bolton-Hunter-[Leu 15]human gastrin-(2–17) to two affinity classes of sites. K d values of the high affinity binding components indicate a 4-fold higher affinity of the receptor for sulfated gastrin than for CCK. Finally, the recombinant receptor is coupled to G proteins and [Ca 2+] i mobilization, and is expressed as a glycoprotein of 82 kDa.

Detection of Cholecystokinin B/Gastrin Receptor mRNA Expressing Cells in the Stomach of Hypergastrinemic Rats.

Enterochromaffin-like (ECL) cells, which are numerous in the oxyntic mucosa of the rat stomach, proliferate in the presence of hypergastrinemia. We investigated the distribution of cells expressing gastrin receptor (GR) in Sprague-Dawley rats in which hypergastrinemia was induced by partial gastric corpectomy. The ECL cell density was determined by immunohistochemical staining for histamine. The expression of GR mRNA was investigated using digoxigenin-labeled complementary RNA probes. The labeling index of the generative cell zone was determined by 3H-thymidine autoradiography. The ECL cell density and the labeling index in the generative cell zone increased in association with increased plasma levels of gastrin after 24 weeks (p<0.05). The expression of GR mRNA was seen not only in ECL, generative, parietal and chief cells, but also in stromal cells of hypergastrinemic rats. The expression of GR mRNA became more marked in the oxyntic mucosa as plasma levels of gastrin increased, and it was suggested that GR mRNA expression acts as one indication in the development of ECL cell hyperplasia.