Mechanisms in regulating the release of serotonin from the perfused rat stomach

The mechanisms regulating the release of serotonin into the portal circulation as well as into the gastric lumen were studied in the isolated vascularly and luminally perfused rat stomach. Immunohistochemical study of the rat stomach showed that serotonin-containing enterochromaffin (EC) cells were densely packed in the antral mucosa, sparsely scattered in the corpus, and not found in the fundus. Such morphological findings suggest that serotonin detected in this study may have originated from antral EC cells. Luminal acidification stimulated the vascular release of serotonin but did not affect the luminal release of serotonin. The basal release of serotonin into the vasculature was 10 times higher than that into the gastric lumen at intragastric pH 2. The vascular release of serotonin is regulated by stimulation from cholinergic nicotinic mechanisms, whereas inhibitory neurotransmitters such as vasoactive intestinal peptide and NO are probably not involved. Somatostatin and peptide YY originating from endocrine cells may exert direct inhibitory effects, possibly via somatostatin and peptide YY receptors on the EC cells, and a cholinergic muscarinic mechanism may exert indirect effects on the vascular release of serotonin via the muscarinic receptor on the endocrine cells.     

Effect of starvation on endocrine cells in the rat stomach

The influence of food deprivation on gastric G- and D-cells and on parietal cells was studied in the rat. In fed controls and groups of rats fasted for 12 and 96 h G-, D- and parietal cell densities, somatostatin and gastrin concentration in antral and fundic specimens and serum gastrin were compared. Gastrin in antral mucosa, serum gastrin, G-cell density as well as antral D-cell density decreased in long-term fasted rats by 52%, 90%, 58% and 42%, respectively. Fundic D-cell density remained unchanged. After 96 h starvation somatostatin concentration slightly increased in antral mucosa (+35%; P less than 0.05), but decreased in fundic mucosa (-40%; P less than 0.05). Parietal cell density was not influenced by prolonged fasting. These findings demonstrate that changes in D-cell morphology and mucosal somatostatin content are not parallel and that the rat gastric D-cell is less dependent on food in the gastric lumen than the G-cell. The unaltered fundic D-cell density reflects the functional activity of gastric D-cell which has also been shown to be independent of the presence or absence of food.     

Serotonin-producing enterochromaffin (EC) cells of gastrointestinal mucosa in dexamethasone-treated rats

The aim of our study was to investigate the morphological, immunohistochemical and ultrastructural changes of rat serotonin-producing enterochromaffin (EC) cells of gastrointestinal mucosa in dexamethasone-treated rats (D). After 12-daily intraperitoneal administration of 2 mg/kg dexamethasone, rats developed diabetes similar to human diabetes type 2. Stomach, small and large intestines were examined. Large serotonin positive EC cells appeared in the corpus mucosa epithelium of D group of rats, although these cells were not present in control (C) rats. Both volume fraction and the number of EC cells per mm(2) of mucosa were significantly increased only in the duodenum. However, the number of EC cells per circular sections of both antrum and small intestine was increased, but reduced both in the ascending and descending colon in D group. The dexamethasone treatment caused a strong reduction in number of granules in the antral EC cells, while it was gradually increased beginning from the jejunum to descending colon. The mean granular content was reduced in the antral EC cells but increased in the jejunal EC cells in D group. In conclusion, the present study showed that morphological changes in gut serotonin-producing EC cells occurred in diabetic rats.     

Proliferative activity of gastric and duodenal endocrine cells in the rat

The replicative activity and migration of gastrin, somatostatin and serotonin cells in rat stomach and duodenum was studied using combined immunocytochemistry and autoradiography after 3H thymidine pulse-labeling. Our results show that a small proportion of gastrin, somatostatin and serotonin immunoreactive cells displays proliferative activity. The overall labeling index ranged from 1.3% for gastric endocrine cells to 3.2% for duodenal endocrine cells. In a pulse chase experiment, labeling indices of immunoreactive cells were estimated at several time intervals after 3H thymidine administration. Significant differences in labeling index were not found. Migration of 3H thymidine labeled endocrine cells towards the luminal surface was not found in the stomach nor in the duodenum. It is concluded that 1) these endocrine cells have replicating activity; 2) the replicative activity of endocrine cells is higher in the duodenum than in the stomach; 3) the various cell types do not show significant differences in replicating activity and 4) endocrine cells did not seem to migrate to the luminal surface of the mucosa along with the other epithelial cells.     

Growth pattern of the polypeptide-YY cell population in the upper digestive tract of the rat during the perinatal period and after weaning

Summary The distribution of polypeptide-YY cells within the gastric and duodenal mucosa of the rat and the development of their populations were examined daily from 3 days before birth until day 8 postpartum and after weaning, on day 25 postpartum, using a precise technique of quantification. Polypeptide-YY cells appeared in the stomach around the 19th day of gestation. They were always more numerous in the antral mucosa and particularly in the pyloric sphincter area than in the fundic mucosa. Immunogold staining at the electron-microscopic level revealed that, in the antrum, polypeptide-YY was colocalised with gastrin in endocrine cells mainly of type G and, more rarely, in cells of intestinal type IG. Comparison of the gastrin and polypeptide-YY cell populations in the same rats indicated that, except at day 6 postpartum, there were fewer gastric polypeptide-YY cells than immunoreactive gastrin cells and that polypeptide-YY cells were 8 times less numerous than gastrin cells at day 25 postpartum. Polypeptide-YY cells were clearly present in the duodenum of the 19-day-old embryo. This population increases with age until day 8 postpartum, then significantly decreases (by 87%) between days 8 and 25 postpartum. Because polypeptide-YY may inhibit secretion of gastric acid, it is possible that the presence of significant population of polypeptide-YY cells in the upper digestive tract during the first postnatal week of life may play a role (endocrine or paracrine) in the decreased acid secretion occurring in the newborn rat.     

八肽胆囊收缩素在猪,大鼠和豚鼠肠道的免疫组织化学定位和分布

实验采用ＡＢＣ免疫组织化学方法研究了八肽胆囊收缩素样免疫反应物质在猪、大鼠和豚鼠肠道的定位与分布,并用相邻切片免疫双标记法观察了它与５－羟色胺的关系,结果表明,ＣＣＫ－８－ＩＲ细胞主要位于肠腺的底部,少数位于绒毛上皮。节段性分布上,在猪可见于从十二指肠到结肠全长的粘膜,大鼠和豚鼠ＣＣＫ－８－ＩＲ细胞则见于从十二指肠至回肠的粘膜,但均以十二指肠密度最高;免疫双标记法证实,在三种动物肠道中均有ＣＣＫ＝     

A-like cells in the rat stomach contain ghrelin and do not operate under gastrin control

Ghrelin is a 28 a.a. gastric peptide, recently identified as a natural ligand of the growth hormone secretagogue receptor (orphan receptor distinct from the receptor for growth hormone releasing hormone). In the present study, radioimmunoassay demonstrated ghrelin-like material in the rat oxyntic mucosa with moderate amounts also in antrum and duodenum. Small amounts were found in the distal intestines and pancreas. Northern blot analysis revealed abundant ghrelin mRNA in the oxyntic mucosa. Immunocytochemistry demonstrated ghrelin-immunoreactivity in endocrine-like cells in the oxyntic mucosa. Such cells occurred in low numbers also in the antrum and duodenum. The rat oxyntic mucosa is rich in endocrine (chromogranin A/pancreastatin-immunoreactive) cells, such as the histamine-rich ECL cells (65-75% of the endocrine cells), the A-like cells (20-25%) and the D cells (somatostatin cells) (10%). The ghrelin-immunoreactive (IR) cells contained pancreastatin but differed from ECL cells and D cells by being devoid of histamine-forming enzyme (ECL cell constituent) and somatostatin (D cell constituent). Hence, ghrelin seems to occur in the A-like cells. The ghrelin-IR cells in the antrum were distinct from the gastrin cells, the serotonin-containing enterochromaffin cells and the D cells. Conceivably, ghrelin cells in the antrum and distally in the intestines also belong to the A-like cell population. The concentration of ghrelin in the circulation was lowered by about 80% following the surgical removal of the acid-producing part of the stomach in line with the view that the oxyntic mucosa is the major source of ghrelin. The serum ghrelin concentration was higher in fasted rats than in fed rats; it was reduced upon re-feeding and seemed unaffected by 1-week treatment with the proton pump inhibitor omeprazole, resulting in elevated serum gastrin concentration. Infusion of gastrin-17 for 2 days failed to raise the serum ghrelin concentration. Omeprazole treatment for 10 weeks raised the level of HDC mRNA but not that of ghrelin mRNA or somatostatin mRNA in the oxyntic mucosa. Hence, unlike the ECL cells, ghrelin-containing A-like cells do not seem to operate under gastrin control.     

The morphometric and immunohistochemical characteristics of the gastric and duodenal mucosa in systemic lupus erythematosus]

Histological, morphometric, and immunohistochemical studies of biopsy specimens from the mucosa of the body and antral portion of the stomach, the bulb and descending portion of the duodenum were performed in 27 children with systemic lupus erythematosis (SLE) and in 12 with chronic gastroduodenitis. The inflammatory infiltrate from SLE patients was found to contain higher levels of young and mature fibroblasts than that from patients with chronic gastroduodenitis, mature fibroblasts being prevalent. The inflammatory changes in the gastric and duodenal mucosa were ascertained to be associated with the progression of SLE. In exacerbation of SLE, the walls of vessels (arterioles) exhibited immune complexes classified mainly as IgG and, to a lesser degree, as IgM. In remission, the luminescence of the vessels decreased. The serum level of immunoglobins did not correlate with their regional production in the gastric and duodenal mucosa.     

Topography of somatostatin cells in the stomach of the rat: Possible functional significance

Summary Somatostatin cells in the stomach of the rat have a characteristic shape and distribution. In the antral mucosa they occur together with gastrin cells and enterochromaffin cells at the base of the glands. In the oxyntic mucosa they are scattered along the entire glands with some predominance in the zone of parietal cells. Throughout the gastric mucosa the somatostatin cells possess long and slender processes that emerge from the base of the cell and end in clublike swellings. Such processes appear to contact a certain proportion of neighbouring gastrin cells in the antral mucosa and parietal cells in the oxyntic mucosa.Exogenous somatostatin given by intravenous infusion to conscious rats counteracted the release of gastrin stimulated by feeding, elevated antral pH or vagal excitation. Gastrin causes parietal cells to secrete HCl and endocrine cells in the oxyntic mucosa to mobilise and synthesise histamine. Somatostatin is known to block the response of the parietal cells to gastrin. In contrast, somatostatin did not block the response of the histamine-storing endocrine cells to gastrin, perhaps because these endocrine cells lack receptors to somatostatin. Conceivably, somatostatin in the gastric mucosa has a paracrine mode of action. The observations of the present study suggest that somatostatin may affect some, but not all of the various cell types in the stomach. Under physiological conditions this selectivity may be achieved in the following ways: 1) Communication may be based on direct cell-to-cell contact. 2) Only certain cell types are supplied with somatostatin receptors.     

Gastrin-releasing peptide: neuronal distribution and spatial relation to endocrine cells in the human upper gut

By using immunocytochemical techniques, we have studied the distribution of gastrin releasing peptide (GRP)-containing neurons as well as the spatial relationship between these neurons and the endocrine cells in the human stomach and duodenum. Moderate numbers of immunoreactive fibers were distributed in the smooth muscle and submucosa of the stomach; they were more rare in the duodenal wall. Numerous GRP-containing nerve fibers were found in the oxyntic mucosa, the antral mucosa harboured only few GRP immunoreactive nerve fibers. The mucosa of the proximal duodenum was found to be virtually devoid of such fibers. Only occasionally did we observe signs of a direct contact between GRP-containing nerve fibers and gastrin and somatostatin cells in the antral mucosa. In the oxyntic mucosa GRP-containing nerve fibers sometimes seemed to contact endocrine cells, including somatostatin cells as well as individual parietal cells. In conclusion, although GRP-containing nerve fibers were quite numerous in the wall of the human upper gastro-intestinal (GI)-tract, we observed a lack of intimate spatial relationship between these fibers and endocrine cells in the antral mucosa, suggesting additive mechanisms to a direct innervation of gastrin cells and somatostatin cells by GRP nerve fibers explaining the physiological effects on hormonal release.     

Occurrence and neonatal development of gastrin immunoreactivity in the digestive tract of the rat

Summary The distribution of gastrin immunoreactivity in the rat gut was examined by immunochemical and immunohistochemical techniques. Gastrin occurs predominantly in the antrum proper, but gastrin is found also in the adjacent part of the oxyntic mucosa and in the duodenum. In the remainder of the gut the gastrin concentration is very low. No gastrin cells and very low gastrin concentrations are observed in the antrum at birth. The gastrin concentration as well as the number of gastrin cells increases progressively with age. The antral gastrin concentration reaches adult or near-adult values 30–40 days after birth.This study was supported by the Swedish Medical Research Council (04 X-1007), by Riksföreningen mot Cancer (660-0 IX), Landsforeningen till Kraeftens Bekampelse, Danish Medical Research Council (512-6) and Fonden for Storkobenhavn, Faeroerne og Gronland.     

Self-renewal of the human gastric epithelium: new insights from expression profiling using laser microdissection

The gastric mucosa is subject to continual bidirectional renewal by differentiation from stem and transit amplifying cells. It was the aim of this study to characterize the self-renewal of the human gastric mucosa and its two major types of glands in the fundus and antrum, respectively. Three characteristic regions (pit, proliferative, and lower neck regions) were isolated from fundic and antral units by the use of laser microdissection, and expression profiles concerning 15 marker genes were generated by RT-PCR analysis. The surface mucous cells (SMCs) of fundic and antral units differed in their expression of at least four secretory genes, i.e., gastric lipase, TFF3, FCGBP, and lysozyme. The maturation of mucous neck cells was shown to occur stepwise, first towards a mucous phenotype followed by a serous differentiation step. Also, a stepwise maturation of both the antral SMCs and antral gland cells was observed. Additionally, the presence of gastric lipase was also demonstrated for the first time in antral gland cells. In conclusion, the different expression profiles of SMCs of the fundic and antral units could be the basis for the different self-renewal rates of fundic and antral SMCs and could influence the spatial organization of the bacterial microbiota within the various parts of the gastric mucosa.     

Regulation of somatostatin-14 and gastrin I binding sites in rat gastrointestinal mucosa by ulcerogenic dose of cysteamine

A single duodenal ulcerogenic dose of cysteamine administered into rats induced time-dependent depletion of immunoreactive somatostatin in the gastric corporeal, antral, and duodenal mucosa with a parallel increase (up-regulation) of somatostatin binding sites. The concentration of somatostatin binding sites returned to the control level in the corporeal mucosa when measured at 24 hrs; however, in the duodenal mucosa there was only a partial return to the control level. Somatostatin binding sites in the antral mucosa did not return to control level even after 24 hrs. Except for the duodenum mucosal immunoreactive gastrin level was unaffected by cysteamine administration, but corporeal mucosal gastrin I binding sites were diminished (down-regulation) after 24 hrs.     

The influence of the different morphological changes on gastric mucosa on somatostatin cell number in antrum mucosa and serum somatostatin

The aim of our paper was to investigate the influence of the different morphological changes on gastric mucosa on somatostatin D-cell number in antral mucosa and serum Somatostatin. We analyzed according to Sydney classification to what extent the severity of gastritis affect the observed hormonal values. somatostatin D-cell number in antral mucosa and serum Somatostatin values were compared between three groups of patients; mild, moderate and severe chronic gastritis. The average number of somatostatin cell in biopsy sample of antrum mucosa was 30.41 +/- 35.38 (N = 17) in the case of middle form, 18.69 +/- 26.65 (N = 56) in moderate and in severe case of chronic gastritis 5.23 +/- 5.93 (N = 7) cells in mm2 of mucosa. The level of somatostatin in the serum of middle form gastritis were 26.43 +/- 28.76, moderate 19.95 +/- 35.93 and severe 17.88 +/- 17.66 pg/mL. In order to determine the number of somatostatin cells in antrum mucosa and serum somatostatin with present morphological changes of mucosa, it might helpful to exclude the patients with non-ulcer dyspepsia, but with the higher risk of premalignant and malignant changes.     

Vesicular monoamine transporters in the rat stomach.

Cellular distribution of vesicular monoamine transporters (VMATs), known to regulate vesicular storage and release of biogenic amines (i.e., catecholamines, serotonin, histamine, etc.), have been studied in the rat stomach using in situ hybridization histochemistry (ISHH) and immunohistochemical (IHC) techniques. 35S-UTP labeled riboprobes showed that mRNAs of both VMATs are expressed in the gastric mucosa. A combination of ISHH and IHC verified that most of the parietal cells (among other epithelial cells) express mRNA of the peripheral type transporter (VMAT1) while enterochromaffin-like cells (ECL) of the fundic mucosa express mRNA of the central type (VMAT2). In addition, with double fluorescent IHC we detected VMAT1 protein in serotoninergic enterochromaffin cells (EC) of the stomach and in gastrin producing G cells of the antral mucosa. Similarly to the fundus, VMAT2 protein was present in ECL cells and in the enteric plexus. Surprisingly, serotonin- and/or histamine-containing cells in the connective tissue compartments of the stomach (i.e., lamina propria and submucosa), immunoreactive for a mast cell specific antigen, displayed neither VMATI nor VMAT2 immunoreactivity. Distribution of VMATs in the rat stomach support our previous observations on aminergic properties of two important gastrointestinal (GI) epithelial cell populations primarily known for other specific secretory products, i.e. dopaminergic properties of acid producing parietal cells and histaminergic properties of gastrin producing G cells. These data emphasize the existence of a non-neuronal, intrinsic aminergic system in the GI tract.     

Mast cells and cells producing alpha-endorphin in the mucosa of the antral section of the stomach

The distribution of mast cells, alpha-endorphine-producing cells (AER-cells) and argyrophilic cells in lamina propria of the antral mucosa was determined quantitatively in 13 normal men. The cells were detected by histochemical and immunohistochemical (PAP) methods. The form and site of AER-cells resembled those of mast cells and mucosal argyrophilic cells (in lamina propria). The authors assume that part of human gastric mucosal cells have argyrophilic properties and contain alpha-endorphine.     

Proenkephalin A Processing in the Upper Digestive Tract: Isolation and Characterisation of Phosphorylated N-Terminally Extended Met-Enkephalin Arg6Phe7 Variants

Previous studies suggest the processing of proenkephalin A in the porcine upper digestive tract might differ from that in the brain. To characterise more precisely some of the products, we have used antibodies to Met-enkephalin Arg6Phe7 (MERF) in radioimmunoassay to monitor the isolation of immunoreactive peptides from extracts of porcine pyloric antral muscle, antral mucosa, and duodenum. Sephadex G50 gel filtration of each extract produced a single broad peak of high-molecular-weight MERF-immunoreactivity. On anion-exchange chromatography the antral muscle MERF-immunoreactivity fractionated into two major peaks, and that from the antral mucosa and duodenum each into four major peaks, suggesting tissue specific processing of proenkephalin A within the porcine gut. Reverse-phase HPLC and Edman degradation analysis revealed that the least acidic antral muscle peptide was a 31-residue N-terminally extended form of MERF that is equivalent to proenkephalin A 209-239. Alkaline phosphatase digestion of the N-terminally extended MERF variants indicated that some of these peptides were modified by phosphorylation. We conclude that there are complex patterns of proenkephalin A processing in the porcine gut, which in part are due to phosphorylation.     

Serum Gastrin and the Antral Mucosa in Atrophic Gastritis

The gastric antral mucosa was studied histologically in 22 patients with atrophic gastritis, of whom 11 had high levels and 11 had normal levels of serum gastrin. The antrum was graded histologically from normal to grade 3 gastritis. All patients with hypergastrinaemia (nine seropositive and two seronegative for parietal cell antibody) had either a normal antrum or minimal (grade 1) antral gastritis. In contrast all but one patient without raised serum gastrin (nine seronegative and two seropositive for parietal cell antibody) had severe (grades 2-3) antral gastritis. Thus circulating gastrin levels observed in patients with gastritis and achlorhydria can be directly related to the presence or absence of antral mucosal damage.Comparison of the histological appearances of the antral mucosa with serum gastrin and parietal cell antibody status has provided a basis for the separation of two distinctive forms of atrophic gastritis.