Effect of gastrin-releasing peptide (GRP) on guinea pig gallbladder contrction in vitro

Few studies have reported the effects of gastrin-releasing peptide (GRP)/bombesin on the guineas pig gallbladder, and the results are contradictory. Because such contradictory results may, in part, be due to technical factors, we investigated the effect of GRP on guinea pig gallbaladder smooth muscle, using a improved horizontal organ bath. The guinea pigs were killed and the gallbladder was removed. Four longitudinal uscle strips (2×12mm) were suspended in Krebs-Ringer solution at 37°C and aerated with 95% O₂ and 5% CO₂. The mechanical activity of the strips was recorded isotonically by displacement-voltage transducers. via L-arms, to which a piezoelectric element with a frequency of 100Hz and movement of 50μm was applied. GRP contracted gallbladder muscle strips dose dependently, but the calculated maximal response was 22.4% and 20.1% of the acetylcholine-and cholecystokinin octapeptide (CCK8)-induced responses, respectively. The GRP-induced contraction was unaffected by the muscarinic blocker, atropine, or by the CCK receptor antagonist, loxiglumide. It is concluded that GRP weakly, but apparently directly, stimulates guinea pig gallbladder contraction.     

Gastrin-releasing peptide messenger ribonucleic acid expression in the hypothalamic paraventricular nucleus is altered by melanocortin receptor stimulation and food deprivation

Gastrin-releasing peptide (GRP) is a bombesin-like peptide widely distributed in the gastrointestinal tract and central nervous system. In the brain, GRP mRNA is located in the hypothalamic paraventricular nucleus (PVN), a region that receives neural input from the arcuate nucleus and plays a critical role in food intake and energy balance. Because GRP neurons are localized in the vicinity of projection sites in the PVN for peptides that participate in energy homeostasis, we investigated whether GRP mRNA expression in the PVN may be sensitive to challenges imposed by either 38 h food deprivation or stimulation of the melanocortin system by the melanocortin 3/4 receptor agonist, melanotan II (MTII). We found that food deprivation significantly decreased GRP mRNA expression, whereas lateral ventricular MTII administration increased GRP mRNA expression in ad libitum-fed rats 4 h after administration. Furthermore, administration of MTII at a dose that reduces 24 h food intake and body weight prevented the decrease in GRP mRNA expression observed in animals that were pair fed to the amount of food consumed by those injected with MTII. These results demonstrate that food deprivation and stimulation of the melanocortin system produce opposing changes in GRP gene expression in the PVN, suggesting that GRP-containing neurons in the PVN may be part of the hypothalamic signaling pathway controlling food intake and energy balance.     

Regulation of gastric function by endogenous gastrin releasing peptide in humans: studies with a specific gastrin releasing peptide receptor antagonist

BACKGROUND AND AIMS: The main goal of our study was to characterise the activity of BIM26226 as a peripheral gastrin releasing peptide (GRP) receptor antagonist in healthy human subjects and to determine if endogenous GRP is a physiological regulator of gastric acid secretion and gastrin release. METHODS: Our study consisted of three parts. In part I, subjects received saline or BIM26226 followed by graded doses of intravenous human GRP in a four period crossover design. In part II, subjects received BIM26226 or saline during oral meal ingestion or modified sham feeding. In part III, subjects received an acidified meal in the presence and absence of BIM26226 in a two period crossover design. In addition, gastrin and somatostatin mRNA were measured in biopsy specimens during saline and BIM26226 infusion. RESULTS: BIM26226 dose dependently inhibited GRP induced acid output. Acid secretion after oral liquid meal intake and sham feeding was significantly inhibited by BIM26226 (p<0.01) whereas plasma gastrin release remained unchanged. Gastrin and somatostatin mRNAs were not significantly different after saline or BIM26226. CONCLUSIONS: BIM26226 is a potent GRP antagonist in humans. Endogenous GRP may be a physiological regulator of gastric acid secretion. Gastrin release does not seem to be under the control of GRP.     

Adiponectin receptor expression is elevated in colorectal carcinomas but not in gastrointestinal stromal tumors

Circulating adiponectin is inversely associated with colorectal carcinoma. However, adiponectin receptor expression has not been examined in normal gastrointestinal tissue, colorectal malignancies, or gastrointestinal stromal tumors (GISTs). We collected 40 colorectal carcinomas and 12 non-tumor colorectal tissue specimens from patients with colorectal cancer, as well as 45 tumor and 13 non-tumor specimens from patients with GIST. Expression and localization of adiponectin receptors (AdipoR1 and AdipoR2) were assessed using immunohistochemistry. We also confirmed expression of adiponectin receptors using rtPCR in matched normal and colorectal cancer specimens obtained from five patients. Finally, we detected adiponectin receptors and assessed adiponectin signaling in three colon cancer cell lines. Adiponectin receptor expression, assessed by either rtPCR or immunohistochemistry, was present in normal tissue and was significantly lower than in colorectal carcinomas. Among carcinomas, 95% displayed positive or strongly positive expression of AdipoR1 and 88% of AdipoR2, versus 8% and 0%, respectively, for non-tumor specimens (P<0.0001). AdipoR1 expression assessed by rtPCR was 1.6-fold higher in tumor than in non-tumor tissue (P<0.05). In addition, we found that adiponectin at physiological concentrations can activate in vitro intracellular signaling pathways in three colon cancer cell lines, expressing both adiponectin receptors 1 and 2. No significant differences in expression of adiponectin receptors in tumor versus non-tumor GI specimens were detected among patients with GIST. Colon cancer cell lines express adiponectin receptors, through which adiponectin activates in vitro intracellular signaling pathways. Adiponectin receptors are also detected in normal GI tissue and their expression is elevated in colorectal carcinomas, but not in GIST.     

胃癌细胞株蛙皮素受体的检测

目的 观察胃癌细胞株ＳＧＣ ７９０１细胞蛙皮素受体ｍＲＮＡ和受体蛋白的表达。方法 （１）利用逆转录聚合酶链反应（ＲＴ－ＰＣＲ）和Ｓｏｕｔｈｅｒｎ ｂｌｏｔ观察胃癌细胞株ＳＧＣ ７９０１细胞蛙皮素受体ｍＲＮＡ的表达；（２）利用交联剂（ＤＳＳ）化学交联增强化学发光（ＥＣＬ）自显影观察胃癌细胞株ＳＧＣ７９０１细胞株受体蛋白的表达。结果 （１）ＲＴ－ＰＣＲ产物经Ｓｏｕｔｈｅｒｎ杂交与预期的蛙皮素受体ｃＤＮ     

Tissue-specific regulation of gastrin-releasing peptide synthesis, storage and secretion by oestrogen and progesterone

In the ovine endometrium, dramatic increases in gastrin-releasing peptide (GRP) mRNA and immunoreactivity are observed during the luteal regression phase of the oestrous cycle (24-fold) and during pregnancy (at least 150-fold). This study sought to determine whether oestrogen and/or progesterone were responsible for the temporal regulation of GRP observed in the uterus. Ovariectomized sheep were divided into four groups (n=4), as follows: 1, untreated; 2, given subcutaneous and intravaginal progesterone implants; 3, given subcutaneous oestrogen implants; and 4, treated with both oestrogen and progesterone. After 10 days, the animals were sacrificed and plasma, pituitary and endometrium were obtained. A fifth group of sheep with intact ovaries was included. Analysis of endometrial GRP-immunoreactivity (GRP-ir) revealed a twofold drop for groups treated with oestrogen, progesterone or both hormones. A dramatic reduction in endometrial GRP mRNA was o! bserved in the group treated with both hormones. GRP-ir was measured in whole pituitaries and found to vary greatly (1.7-53.7 pmol/g tissue) within all groups of ovariectomized animals. There were no significant differences between any of the five groups. A significant reduction in circulating GRP-ir was observed after 10 days of treatment with either oestrogen or progesterone. These studies demonstrate that, in sheep, the synthesis, storage and secretion of GRP are differentially affected by oestrogen and progesterone. Regulation appears to be tissue specific since GRP content in the pituitary is unchanged by oestrogen or progesterone whereas GRP expression in the endometrium is inhibited. Changes in GRP mRNA expression did not correlate with changes in endometrial expression of mRNA for oestrogen receptor alpha, oestrogen receptor beta and the progesterone receptor. This study is the first reported demonstration that expression of the GRP gene can be influenced by the presence of ovarian steroids, with the conclusion that oestrogen and/or progesterone act as negative regulators of endometrial GRP expression.     

精氨琥珀酸裂解酶及合成酶在人胃癌组织中表达的意义

目的 探讨精氨琥珀酸裂解酶(ASL)及精氨琥珀酸合成酶(ASS)mRNA在人胃癌组织中的表达.方法 收集胃癌组织15例及相应癌旁正常组织12例,采用RT-PCR方法分别检测其中ASL及ASS mRNA的表达,了解胃癌组织与癌旁正常组织中可能存在的ASS及ASL表达差异.结果 胃癌组织中ASS mRNA的表达低于正常组织,具有统计学差异(P<0.05);但ASL的表达与正常组织相比无显著性差异.结论 胃癌组织中ASS mRNA表达水平下降,提示了精氨酸耗竭原理用于胃癌治疗的可行性.     

Distribution of gastrin-releasing peptide (GRP)-like immunoreactivity in the rat

Rat tissues were examined for gastrin-releasing peptide (GRP)-like immunoreactivity, using carboxy-terminus-specific antibody made against GRP (19-27), which is thought to be the biologically active site and to be common among species. The distribution of GRP-like immunoreactivity in the rat was similar to that of bombesin-like immunoreactivity. Sephadex G 50 chromatography revealed two peaks of GRP-like reactivity in the rat stomach. Immunohistochemical studies using the antiserum to GRP (19-27) revealed numerous nerve fibers in the mucosa of the rat stomach. In the antral mucosa, GRP-containing nerves were present mainly around the base of the antral glands. Some GRP-containing nerves were in contact with gastrin-containing cells and somatostatin-containing cells. GRP-containing nerve fibers were numerous in the middle portion of the oxyntic gland, where somatostatin-containing cells were also detected. None of the endocrine cells stained positively with anti-GRP serum. These results support the hypothesis that GRP is a neurotransmitter in the stomach and that the peptide plays a physiological role in the gastrointestinal tract.     

Molecular characterization and distribution of motilin family receptors in the human gastrointestinal tract

Background Motilin and ghrelin have been recognized as important endogenous regulators of gastrointestinal motor function in mammals, mediated respectively by the motilin receptor and by the closely related ghrelin receptor. The aims of this study were to explore the distribution of motilin and ghrelin receptors along the human gastrointestinal tract and to establish the molecular nature of the human motilin receptor. Methods Post mortem and surgical human tissue specimens with no hemorrhage, necrosis, or tumor were obtained from various parts of the gastrointestinal tract. We analyzed levels of expression of mRNA for motilin and ghrelin receptors and examined their molecular identities. Portions of some specimens were also studied by immunohistochemistry for expression of the motilin and ghrelin receptor. Results The long form of the motilin receptor, but not the short form, was expressed in all parts of the gastrointestinal tract, and expressed at higher levels in muscle than in mucosa. Motilin receptor immunoreactivity was present in muscle cells and the myenteric plexus, but not in mucosal or submucosal cells. In contrast, ghrelin receptor mRNA was expressed equally in all parts of the gastrointestinal tract, with similar levels of expression in mucosal and muscle layers. Conclusions Both the motilin and ghrelin receptors are expressed along the human gastrointestinal tract, but they have clearly distinct distributions in regard to both level and layer. The diffuse muscle expression of the motilin receptor, at both the levels of the gene and the protein product, along the entire gastrointestinal tract makes it a useful potential target for motilide drugs for dysmotility.     

Blockade of GRP receptors inhibits gastric emptying and gallbladder contraction but accelerates small intestinal transit

BACKGROUND & AIMS: This study was designed to characterize [D-F(5)Phe(6)D-Ala(11)]Bn(6-13)OMe (BIM26226) as a gastrin-releasing peptide (GRP)-preferring bombesin receptor antagonist and to determine whether GRP physiologically regulates gastrointestinal motility. Intravenous BIM26226 (5-500 microg. kg(-1). h(-1)) inhibits GRP-induced gallbladder contraction and plasma cholecystokinin (CCK) release in a dose-dependent fashion. METHODS: Gastric emptying and small bowel transit of a solid meal were quantified using scintigraphy. Meal-stimulated gallbladder contraction was measured by sonography in a 2-period crossover design. RESULTS: Intravenous BIM26226 potently inhibited gastric lag time (114 +/- 7 vs. 41 +/- 6 minutes [control]) and gastric emptying rate (0.11 +/- 0.02%/min vs. 0.26 +/- 0.04%/min [control]), whereas concomitant infusion of BIM26226 accelerated small bowel transit time (153 +/- 41 vs. 262 +/- 20 minutes [control]). A continuous liquid meal perfusion into the duodenum induced complete gallbladder contraction (t(50%), 35 +/- 4 minutes), which BIM26226 inhibited significantly (t(50%), 64 +/- 8 minutes). BIM26226 did not alter plasma CCK response, indicating that circulating CCK did not mediate these effects. CONCLUSIONS: These data show that BIM26226 is a potent antagonist of exogenous and endogenous GRP and suggest that GRP is a major physiologic regulator of gastric emptying, small bowel transit, and gallbladder contraction.     

特殊部位肝癌的腹腔镜下射频消融治疗

目的探讨腹腔镜下射频消融术（LRFA）在特殊部位肝癌治疗中的临床疗效和安全性。方法对2010年1月-2011年12月我院39例经螺旋CT证实的肝癌患者实施LRFA临床资料回顾分析。单病灶者25例,2个病灶者14例,共计53个病灶,分别位于肝脏表面、膈顶部、心包及毗邻胆囊、胃肠的肝肿瘤,肿瘤平均直径为3cm。结果39例患者均顺利完成手术,单病灶LRFA平均时间为30min,平均总手术时间为45min。未出现腹腔出血,胃肠道损伤,膈肌损伤及肝功能衰竭等严重并发症。术后一个月螺旋CT增强扫描证实,病灶完全坏死率达100％。随访12～24个月,2例发现肝内新病灶,4例消融部位复发,采用TACE或再次腹腔镜下射频消融治疗。结论LRFA安全性好、恢复快、疗效确切,已成为包括位于特殊部位肝癌微创治疗的主要手段。     

Isolation and characterisation of the ovine gastrin-releasing peptide gene; abundant expression in the pregnant uterus and selective expression in fetal tissues

High concentrations of a peptide related to gastrin-releasing peptide (GRP) are produced in the utero-placental unit of the human and sheep and secreted into the general circulation. This suggests an endocrine role in addition to its role as a neurotransmitter/neuromodulator. The GRP is larger than the previously described form GRP(1-27) but it is not known whether the larger form is the product of a related GRP-like gene or differences in post-translational processing. We have therefore cloned the gene for the sheep homologue of the GRP gene and determined its distribution. Only a single GRP gene was found in the sheep. This had a similar organisation to the human GRP gene with three exons and two introns. The larger form of GRP in the pregnant endometrium therefore appears to be the result of an alteration in processing of the GRP prohormone. The expression of GRP mRNA in the pregnant uterus was extraordinarily high comprising one-third of all mRNA synthesised by the pregnant endometrium. As the endometrial GRP mRNA arises solely from the glandular epithelium, the localised synthesis of GRP mRNA would be far higher. GRP mRNA was expressed in a wide variety of fetal tissues (fundus, colon, jejunum, ileum, duodenum, kidney, adrenal, lung, heart and pancreas) with a corresponding presence of GRP immunoreactivity. The expression of GRP in the fetal lung was biphasic with peaks at mid-term and near parturition but none in the adult supporting the concept of a specific developmental role of GRP in the lung.     

Altered Mucin Core Peptide Expression in Acute and Chronic Cholecystitis

Human mucin genes include membrane-bound mucins (MUC1, MUC3, MUC4) and secretory mucins (MUC2, MUC5AC, MUC5B, MUC6). Our aim was to determine mucin gene expression in human gallbladder cell lines, normal gallbladder from liver donors (N = 7) and surgical specimens with mild chronic cholecystitis (N = 29), chronic cholecystitis (N = 48), and acute and chronic cholecystitis (N = 27). MUC1 mRNA was ubiquitous; however, only rare MUC1 immunoreactivity was detected. MUC3, MUC5AC, MUC5B, and MUC6 mRNA were present in all gallbladder specimens and cell lines examined. Prominent MUC3, MUC5AC, MUC5B, and MUC6 immunoreactivity was present in 86–100% of normal gallbladders. The frequency of MUC5AC reactivity was decreased in specimens with acute cholecystitis (P < 0.05). In contrast, MUC2-reactivity was absent in normal gallbladder and present in 53.8% of acute cholecystitis specimens (P < 0.05). Surface epithelium is characterized by MUC3, MUC5AC, and MUC5B, whereas deeper mucosal folds display MUC5B and MUC6 immunoreactivity. Gallbladder epithelium demonstrates a unique and diverse pattern of mucin core proteins that becomes altered with increasing degrees of inflammation.