Gastrin

Gastrin is the most important peptide in the regulation of gastric acid secretion. This communication reviews important new developments in our knowledge of its synthesis, action, and pathophysiology. The gene for human gastrin has been isolated, and it encodes a pre-pro-gastrin which is a 101-aminoacid peptide containing within it the structure of big gastrin (G34) with a C-terminal glycine extension. Post-translational processing by alpha-amidation of the glycine-extended progastrin results in generation of the active forms of the peptide (G34, G17). When gastrin binds to its receptor on the parietal cell, phosphatidylinositol biphosphate (IP2) in the plasma membrane is converted to inositol 1,4,5-triphosphate (IP3), which acts as the secondary intracellular messenger to increase intracellular calcium and initiate the process that eventually leads to acid secretion. Although an abnormality in gastrin release or action is not thought to be crucially important in the genesis of duodenal ulcer, these patients nevertheless demonstrate increased postprandial gastrin release, and a greater sensitivity of their parietal cells to gastrin. Hypergastrinemia is the cause of peptic ulceration in the Zollinger-Ellison syndrome, in primary gastrin cell hyperplasia or hyperfunction, and in the retained antrum syndrome. Ulcerogenic hypergastrinemia must be distinguished from hypergastrinemia that is secondary to hypoacidity or anacidity, as is seen in atrophic gastritis or postvagotomy.     

Sex-related Differences in Gastrin Release and Parietal Cell Sensitivity to Gastrin in Healthy Human Beings

We compared serum gastrin concentrations and gastric acid secretion basally and in response to a mixed meal in age-matched women and men. Women had significantly higher basal serum gastrin concentrations (P < 0.01) and two- to threefold higher food-stimulated serum gastrin concentrations (P < 0.001) than men. Basal and food-stimulated serum gastrin concentrations in women did not fluctuate significantly during the menstrual cycle. Sex-related differences in food-stimulated serum gastrin concentrations were not due to differences in antral pH because pH after the meal in women and men had been kept constant at 5.0 by in vivo intragastric titration with sodium bicarbonate.     

雷贝拉唑、血清胃泌素与十二指肠球部溃疡

通过分析雷贝拉唑、血清胃泌素与十二指肠球部溃疡的关系,阐述雷贝拉唑治疗十二指肠球部溃疡的效果及雷贝拉唑在治疗十二指肠球部溃疡的过程中对胃泌素的影响,探讨雷贝拉唑、血清胃泌素对DU发展及愈合的作用。     

Gastrin stimulates gastric mast cells in rabbits

In a previous study we demonstrated that in human gastric mucosa tryptase was localized only in mast cells and that its levels were correlated with serum gastrin, suggesting a link between gastrin action and mucosal mast cell function. The aim of the present study was to discover whether pentagastrin injection could stimulate gastric mucosal mast cells in rabbits. Ten female rabbits (group S) were injected s.c. with pentagastrin (10 μg/kg); another group of ten animals (group C) was injected s.c. with an equal volume of saline solution. One hour after the injection the rabbits were sacrificed and their stomachs removed. Antrum (A), corpus (C) and fundus (F) mucosal homogenates were assayed for total protein, tryptase, pepsinogen A (PGA), histamine and gastrin. Histamine tissue levels were significantly lower in group S than in group C in the antrum (Mann-Whitney test: U=82,P<0.01) and in the corpus (U=83,P<0.005). Tryptase levels were significantly higher in group S than in group C in all gastric areas (antrum: U=95,P<0.001; corpus: U=85,P<0.005 and fundus: U=75,P<0.05). Total protein PGA and gastrin did not vary significantly between groups. In group C, no signficant correlations were found among the five parameters. In group S, corpus tryptase was correlated with fundus tryptase (Spearman'sr=0.831,P<0.01). The same relationship was observed for histamine (r=0.672,P<0.05). In group S, antrum gastrin was inversely correlated with antrum tryptase (r=0.903,P<0.001), and with corpus PGA (r=?0.806,P<0.05). This study demonstrates that bolus pentagastrin administration stimulates gastric mucosal mast cells in the rabbit.     

Gastrin receptors on isolated canine parietal cells.

The receptors in the fundic mucosa that mediate gastrin stimulation of acid secretion have been studied. Synthetic human gastrin-17-I (G17) with a leucine substitution in the 15th position ( [Leu15]-G17) was iodinated by chloramine T; high saturable binding was found to enzyme-dispersed canine fundic mucosal cells. 127I-[Leu15]-G17, but not 127I-G17, retained binding potency and biological activity comparable with uniodinated G17. Fundic mucosal cells were separated by size by using an elutriator rotor, and specific 125I-[Leu-15]-G17 binding in the larger cell fractions was highly correlated with the distribution of parietal cells. There was, however, specific gastrin binding in the small cell fractions, not accounted for by parietal cells. Using sequential elutriation and stepwise density gradients, highly enriched parietal and chief cell fractions were prepared; 125I-[Leu15]-G17 binding correlated positively with the parietal cell (r = 0.98) and negatively with chief cell content (r = -0.96). In fractions enriched to 45-65% parietal cells, specific 125I-[Leu15]-G17 binding was rapid, reaching a steady state at 37 degrees C within 30 min. Dissociation was also rapid, with the rate similar after 100-fold dilution or dilution plus excess pentagastrin. At a tracer concentration from 10 to 30 pM, saturable binding was 7.8 +/- 0.8% per 10(6) cells (mean +/- SE) and binding in the presence of excess pentagastrin accounted for 11% of total binding. G17 and carboxyl terminal octapeptide of cholecystokinin (26-33) were equipotent in displacing tracer binding and in stimulating parietal cell function ( [14C]aminopyrine accumulation), whereas the tetrapeptide of gastrin (14-17) had a much lower potency. Proglumide inhibited gastrin binding and selectively inhibited gastrin stimulation of parietal cell function. Canine parietal cells have specific receptors for gastrin that mediate stimulation of parietal cell function. Gastrin receptors were undetectable on chief cells, and yet present on another smaller mucosal cell(s).     

Gastrin/CCK与癌基因/抑癌基因之间的相互作用研究进展

胃泌素(Gastrin)和胆囊收缩素(Choleeystoknin，CCK)在近20年里作为单纯消化道激素的概念发生了巨大变化。就成年机体而言，Gastrin／CCK基因平常在G细胞和Ⅰ细胞以外的消化道非内分泌细胞中仅低水平表达、分泌微量未成熟的Gastrin／CCK前体，但在其来源肿瘤的发生、发展过程中，     

Stimulation of Gastrin Secretion and Synthesis in Antral Organ Culture

The purpose of the present study was to examine stimulation of gastrin release and the synthesis of gastrin directly by measurement of incorporation of [(3)H]tryptophan into gastrin in rat antral mucosal explants maintained in organ culture. Gastrin synthesis and secretion were assessed simultaneously at intervals over the 24-h duration of explant culture. Antral mucosal explants from fed female Wistar rats (4-5 wk, 100-150 g) were cultured at 37 degrees C (95% O(2)/5% CO(2)) in medium containing 70% Trowell-T8 and 10% NCTC-135 without unlabeled tryptophan, 10% dialyzed fetal calf serum and [(3)H]tryptophan (100 muCi/ml). Antral tissue was harvested at regular intervals during 24-h culture periods. Incorporation of [(3)H]tryptophan into immunoreactive gastrin was determined by techniques utilizing double-antibody immunoprecipitation. Antral tissue protein synthesis was assessed by measurements of incorporation of [(3)H]tryptophan into tissue protein of cultured antral explants. In paired experiments, gastrin synthesis and secretion in the presence of dibutyryl cAMP (DBCAMP) were compared to those observed under control conditions. Gastrin and protein specific activity progressively increased with time. Gastrin specific activity at 30 min increased from 3.3+/-0.5 (SEM) to 55.2+/-10.6 fmol [(3)H]tryptophan/pmol gastrin (or from 1.57+/-0.48 to 26.28+/-5.05 pmol [(3)H]tryptophan/mug gastrin) at 24 h: specific activity of antral tissue protein at 30 min increased from 33.6+/-8.4 to 1,660+/-236 fmol [(3)H]tryptophan/mug protein at 16 h. Culturing of explants for 4 h in the presence of cycloheximide (100 mug/ml) inhibited both gastrin synthesis and protein synthesis by greater than 90 and 95%, respectively. DBCAMP (10 mM) significantly increased both the synthesis and secretion of antral gastrin when compared with control cultured explants. Results of these experiments provide direct demonstration of gastrin synthesis by rat antral mucosal explants in organ culture, indicate that both gastrin and total antral protein synthesis are inhibited by cycloheximide, and demonstrate DBCAMP-induced stimulation of both gastrin synthesis and secretion, suggesting the potentially important role of cyclic AMP in gastrin cell function.     

血清胃蛋白酶原、促胃液素对胃癌的诊断价值

目的研究血清胃蛋白酶原Ⅰ(PG I)、胃蛋白酶原Ⅱ(PGⅡ)及促胃液素(GS)与胃癌发生的关系,探讨检验血清PGⅠ,PGⅡ,GS对胃癌的诊断价值。方法采用免疫放射分析法(IRMA)和放射免疫分析法(R IMA)检测36例胃癌患者、23例胃良性病、11例萎缩性胃炎和34例正常人血清蛋白酶原、促胃液素水平并进行比较。结果胃癌患者血清PGⅠ,PGⅡ的水平显著低于胃良性病和正常人组(P<0.05),而血清GS水平显著高于胃良性病和正常人组(P<0.05),其中不同分化程度间差异不明显(P>0.05),术后血清PGⅠ,PGⅡ,GS水平显著低于术前水平(P<0.05),复发组的水平显著高于术后未复发组(P<0.05)。结论检测血清PGⅠ,PGⅡ,GS对胃癌的诊断及区别胃良性病具有较高的临床价值。