Depletion of Enterochromaffin-Like Cell Histamine Increases Histidine Decarboxylase and Chromogranin: A mRNA Levels in Rat Stomach by a Gastrin-Independent Mechanism

Background: Gastrin activates histidine decarboxylase (HDC) and increases HDC and chromogranin A (CGA) mRNA levels in histamine-producing enterochromaffin-like (ECL) cells in the rat stomach. We have studied how histamine depletion by subcutaneous infusion of the HDC inhibitor α-fluoromethyl-histidine (α-FMH) affects how ECL cells respond to hypergastrinemia in terms of HDC and CGA mRNA levels. Methods: In one experiment rats received α-FMH for 24 h. In another experiment rats received α-FMH, omeprazole (perorally), or a combination of the two drugs for 10 days. In a third experiment antrectomized rats were treated with α-FMH for 48 h. The circulating gastrin level, oxyntic mucosal histamine concentration, HDC activity, and HDC and CGA mRNA levels were determined. Results: α-FMH for 24 h increased the HDC and CGA mRNA levels without increasing the serum gastrin concentration. α-FMH for 10 days increased the serum gastrin concentration twofold. α-FMH + omeprazole resulted in the same serum gastrin concentration as after omeprazole alone (eightfold increase). HDC mRNA levels were higher after α-FMH + omeprazole than after omeprazole alone. α-FMH alone induced an HDC mRNA level that was similar in magnitude to that observed after omeprazole, although the serum gastrin concentration after α-FMH was much lower. In antrectomized rats α-FMH increased the HDC and CGA mRNA levels without increasing the serum gastrin concentration. Conclusion: ECL-cell histamine depletion will increase mRNA levels for HDC and CGA by a gastrin-independent mechanism, possibly involving abolished histamine autofeedback inhibition.     

Hypercholecystokininemia Produced by Pancreaticobiliary Diversion Causes Gastrin-Like Effects on Enterochromaffin-Like Cells in the Stomach of Rats Subjected to Portacaval Shunting or Antrectomy

Gastrin and possibly cholecystokinin (CCK) control the activity and growth of the histamine-containing endocrine cells, the enterochromaffin-like (ECL) cells, in the oxyntic mucosa of the rat. Portacaval shunting (PCS) is known to activate the ECL cells through as yet unknown mechanisms. PCS also exaggerates the ECL cells' response to gastrin, whereas antrectomy causes hypotrophy and hypoplasia of the ECL cells. A recent study showed that the ECL cells failed to respond to sustained hyperCCKemia caused by pancreaticobiliary diversion (PBD). In the present study we investigated whether PBD-produced hyperCCKemia influenced the effects of PCS or antrectomy on the ECL cells. The results show 1) that hyperCCKemia raised the histidine decarboxylase (HDC) activity of the ECL cells in PCS rats but not in control rats, and the CCK-A receptor blockade failed to prevent the enzyme activation; and 2) that PBD prevented the ECL cell hypoplasia and the decrease in HDC activity induced by antrectomy. The findings suggest that under special circumstances endogenous CCK may stimulate the ECL cells.     

Trophic Effects in the Acid-Producing Part of the Rat Stomach after Pyloric Stenosis

Background: Pyloric stenosis produces gastric hypersecretion and is thought to stimulate the growth of the gastric mucosa in the rat, the dog, and man. However, the mechanisms behind the hypersecretion and the trophic effect of pyloric stenosis are little known. The purpose of the present study was to examine whether the postulated trophic effects described include growth of the histamine-producing enterochromaffin-like (ECL) cells and whether circulating gastrin can be held responsible.

Methods: Pyloric stenosis was produced in rats by tying a ligature around the pylorus, thereby narrowing the passage through the sphincter. The animals were left for 4 to 12 weeks.

Results: The operation dilated the stomach, increased the serum gastrin concentration approximately twofold, and increased the oxyntic mucosal weight, volume, and surface area but not the mucosal thickness and total DNA content. The interglandular space was increased, and the DNA concentration was reduced. The density of the ECL cells (that is, the number of ECL cells per visual field) was reduced at 4 weeks and back to control values at 8 and 12 weeks. The calculated total volume of the ECL cell population was unchanged at first but showed a less than twofold increase 12 weeks after the operation. The volume density of the ECL cells (that is, the proportion of the mucosa made up of ECL cells) was reduced at 4 and 8 weeks and was back to normal at 12 weeks. The ECL cells are rich in histidine decarboxylase (HDC); whenever the cells are stimulated, the enzyme activity increases. The HDC activity in the oxyntic mucosa was reduced at first and returned to control values 12 weeks later.

Conclusions: Pyloric stenosis per se does not affect the total number of oxyntic mucosal cells but causes the ECL cell population to grow somewhat, probably because of the moderate hypergastrinemia. Interestingly, however, there was no increase in the HDC activity, suggesting that the ECL cells are not much activated by the operation.     

Classical Barrett Esophagus Contrasted with Barrett-Type Epithelium at Normal-Appearing Esophagogastric Junction: Comparison of Demographic,Endoscopic, and Histologic Features

Background: Incomplete intestinal metaplasia or specialized columnar epithelium (SCE) is the histologic hallmark of Barrett esophagus (BE), but it may also occur at a normal-appearing gastroesophageal junction without BE. We studied whether differences occur between BE patients and those with SCE at the squamocolumnar junction but without BE (abbreviated JSCE), in terms of endoscopic and histologic signs of gastroesophageal reflux disease (GERD) and Helicobacter pylori gastritis. Methods: A total of 1059 consecutive patients referred for endoscopy in one hospital district in Finland were enrolled in the study. Biopsy specimens (at least two from each site) were obtained from the gastric antrum and the corpus of the stomach and from the esophagogastric junction and distal esophagus. Results: Classical BE was detected in 25 (2%) and JSCE in 99 (9%) patients. Dysplasia in the metaplastic mucosa was observed in six BE patients but in none of the JSCE patients (P < 0.001). In multivariate analysis the independent risk factors for BE were endoscopic erosive esophagitis (odds ratio (OR), 6.08; 95% confidence interval (CI), 2.50-14.82), male sex (OR, 3.02; 95% CI, 1.20-7.65), and age (OR, 1.02 per year; 95% CI, 1.00-1.06). The independent risk factors for JSCE were endoscopic erosive esophagitis (OR, 1.88; 95% CI, 1.08-3.29) and age (OR, 1.03; 95% CI, 1.02-1.05) but not H. pylori infection (OR, 1.57; 95% CI, 0.83-2.97) or chronic gastritis (OR, 0.88; 95% CI, 0.44-1.75). In univariate analysis, however, JSCE was associated with antral-predominant atrophic gastritis (77% H. pylori-positive). Unlike in JSCE patients, male sex strongly predominated among BE patients (P = 0.01). The mean ages of BE and JSCE patients did not differ. Conclusions: Both BE and JSCE without BE increase in prevalence with age, and both associate with endoscopic erosive esophagitis but not with H. pylori gastritis. However, because of the marked sex disparity, JSCE cannot be a direct precursor of BE, and some factors other than GERD alone also play a role in the pathogenesis of BE. Compared with BE, dysplasia is a rare finding in JSCE, and endoscopic surveillance with biopsy specimens from JSCE patients without dysplasia is not recommended.     

Argyrophil Cells,Mast Cells,and Histamine in the Fundic Mucosa of Antrectomized Patients

Fasting gastrinemia, fundic argyrophil cell density, mast cell number, basal fundic histamine content and histidine decarboxylase activity were determined in 20 antrectomized patients and 20 control subjects. Fasting gastrinemia and fundic argyrophil cell density were significantly lower in antrectomized patients than in controls, whereas fundic mast cell number, basal histamine content, and histidine decarboxylase activity did not differ significantly between the two groups. In antrectomized patients the basal fundic histamine content appears related to the fundic mast cell number, as a consequence of the reduced effect of gastrin on argyrophil cells.     

Gastrin Produces an Immediate and Dose-Dependent Histamine Release Preceding Acid Secretion in the Totally Isolated,Vascularly Perfused Rat Stomach

Increasing doses of gastrin 1–17 (Gl-17) were administered to totally isolated, vascularly perfused rat stomachs prestimulated with the phosphodiesterase inhibitor isobutyl methylxanthine (IMX). Vascular and luminal histamine outputs and luminal acid output were monitored at short intervals. (31–17 induced an immediate histamine release to the vascular perfusate, preceding the increase in acid secretion by approximately 10 min. Vascular histamine output increased from a base line (IMX only) of 4.0 ± 0.4 to a maximum of 34.5 ± 7.3 nmol/60 min (mean ± SEM) after 1040 pM G1–17, and acid output from 8.0 ± 2.8 to 61.5 ± 7.0 μmo1/60 min after 520 pM GI-17. Acid output was correlated to vascular histamine release (r = 0.64. p < 0,001). Gastrin produced a histamine release giving gastric venous concentrations of the same magnitude as the concentration of histamine necessary to induce a comparable acid response. Histamine release to the lumen, on the other hand, paralleled the acid secretion in time, suggesting it to be a passive phenomenon secondary to acid secretion. Thus, the present study for the first time shows that gastrin induces vascular histamine release of such a magnitude that this substance could be the mediator of the gastrin effect on acid secretion.     

The Effects of Vagotomy on the Gastric Mucosa of the Rat

In order to determine the effects of vagotomy on the gastric mucosa, the operations of pyloroplasty and vagotomy, pyloroplasty alone, and a sham operation were carried out in rats, and the parietal and peptic cell populations of the stomach were estimated in each animal. From the differences detected between the three groups it was concluded that vagotomy significantly reduced the average number of peptic cells per unit area of the mucosa (33 %), the total peptic cell population (34 %), and the height of the mucosa (19 %). Pyloroplasty alone did not exert any significant effects although it tended to reduce the total parietal cell population.     

Effect of Short- and Long-Term Treatment with Omeprazole on Cell Cycle Distribution in the Gastric Mucosa: Results of a Flow Cytometric Study

Omeprazole may exert an effect on gastric mucosal proliferation by inhibiting gastric acid secretion and increasing serum gastrin levels. It may also influence the kinetics of endocrine cells and the oxyntic mucosa. The aim of the present study was to evaluate the cell cycle in different gastric compartments following short- (1 month) and long-term (6 months) administration of two different dosages of omeprazole by means of a flow cytometric method. We also determined serum gastrin levels at the same time. No differences in cell cycle distribution of the antrum, body, and fundus were found in the two different dosage groups after 1 month of therapy, considering the synthetic phase (S-phase) of the cell cycle. A statistically significant increase in S-phase was reported after long-term therapy in the mucosa of the fundus and body of the stomach in both groups. Gastrin levels showed no clear correlation with cell cycle distribution variables. We postulate a proliferative adaptation of the oxyntic mucosa to long-term drug administration not mediated by gastrin influence.     

Dexamethasone Damages the Rat Stomach but Not Small Intestine During Inhibition of COX-1

We previously reported that inhibition of both COX-1 and COX-2 is required for the gastrointestinal ulcerogenic properties of nonsteroidal anti-inflammatory drugs (NSAIDs). Inhibition of COX-1 up-regulates COX-2 expression, and the prostaglandins (PGs) produced by COX-2 help to maintain the mucosal integrity during inhibition of COX-1. In the present study we investigated whether dexamethasone damages rat gastrointestinal mucosa during inhibition of COX-1 and further developed the idea that COX-2 expression is a key event in the ulcerogenic actions of NSAIDs. Dexamethasone was given p.o. in the absence or presence of SC-560 (a selective COX-1 inhibitor), and the stomach or intestine was examined 8 or 24 hr later, respectively. Neither dexamethasone nor SC-560 alone damaged the gastrointestinal mucosa. In the presence of SC-560, however, dexamethasone damaged the stomach but not small intestine. SC-560 decreased PGE₂ levels in both tissues, with a gradual recovery accompanying the up-regulation of COX-2 expression, and both the recovery of PGE₂ levels and the expression of COX-2 were inhibited by dexamethasone. In the animals treated with SC-560, iNOS expression was up-regulated in the intestinal but not the gastric mucosa, and this response was also inhibited by dexamethasone. These results suggest a risk from steroid therapy in the stomach when COX-2 expression is up-regulated. Dexamethasone does not provoke damage in the intestine, despite inhibiting the up-regulation of COX-2 expression under conditions of PG deficiency; at least one of the reasons is that this agent prevents the expression of iNOS, a major factor in the pathogenesis of intestinal lesions.     

Epigallocatechin Gallate Does Not Accelerate the Early Phase of Liver Regeneration After Partial Hepatectomy in Rats

Background

Two-thirds partial hepatectomy (PHx) is an established model for the study of liver regeneration after resection. This process is accompanied by oxidative stress.

Aims

In our study, we tested the effect of epigallocatechin gallate (EGCG), a green tea antioxidant, on the early phase of liver regeneration after PHx.

Methods

Male Wistar rats were divided into five groups: (I) laparotomy + water for intraperitoneal injections, (II) laparotomy + EGCG 50 mg/kg body weight, (III) PHx + water for injections, (IV) PHx + EGCG 20 mg/kg and (V) PHx + EGCG 50 mg/kg, for 3 consecutive days. The rats were killed 24 h after surgery. Biochemical analysis of rat sera was performed. Histological samples were stained with hematoxylin & eosin and bromodeoxyuridine (BrdU). In hepatectomized rats, we also measured plasma malondialdehyde, tissue malondialdehyde, glutathione and cytokines levels, the activity of caspases 3/7, expression of Nqo-1 and HO-1 genes at the mRNA level, and expression of p21, p-p27 and p-p53 genes at the protein level.

Results

We observed lower accumulation of BrdU in group V when compared to groups III and IV. The activity of caspases 3/7 and expression of p-p53 were lower in group V than in groups III and IV. Tissue levels of IL-6 were lower in group V when compared to group III. Significant differences were not noted in other parameters.

Conclusions

Administration of EGCG did not stimulate early phase liver regeneration in rats after PHx. There was even lower DNA synthesis in the group treated with a high dose of EGCG.     

Effects of omeprazole and pirenzepine on enterochromaffin-like cells and parietal cells in rat stomach

Purpose. The purpose of this study was to investigate the mechanism of the regulation of histamine synthesis in enterochromaffin-like cells, chemically and structurally, by treatment with omeprazole and pirenzepine. Methods. The ultrastructures of enterochromaffin-like cells and parietal cells were examined in rats treated with oral omeprazole (20 mg/kg) or intraperitoneal pirenzepine (1 mg/kg) administration. Serum gastrin concentrations, mRNA levels of H⁺-K⁺-ATPase and histidine decarboxylase, and the fundic concentrations of somatostatin and histamine were determined. Results. Pirenzepine treatment suppressed omeprazole-induced increases in serum gastrin levels and mRNA levels of H⁺-K⁺-ATPase and histidine decarboxylase. Pirenzepine also decreased omeprazole-induced increases of histamine concentration in fundic mucosa. Pirenzepine elevated somatostatin mRNA level, previously decreased by omeprazole treatment, in fundic mucosa. In the cytoplasm of enterochromaffin-like cells, omeprazole markedly reduced the numbers of vesicles and granules, but significantly increased their diameters, whereas pirenzepine treatment changed neither of these features. The densities and diameters of both vesicles and granules produced by treatment with omeprazole and pirenzepine were between those produced by treatment with omeprazole alone and pirenzepine alone. Conclusions. Omeprazole-induced hypergastrinemia and pirenzepine-induced somatostatin synthesis play important roles not only in histamine synthesis but also in ultrastructural changes in enterochromaffin-like cells. Received: September 13, 2000 / Accepted: January 12, 2001     

Degranulation of Mast Cells in the Chick Chorioallantoic Membrane Does Not Increase Macromolecular Extravasation During Normal Angiogenesis

Objective : To test the hypothesis that stimulation of mast cell degranulation during normal angiogenesis in the chick chorioallantoic membrane (CAM) serves to acutely activate macromolecular transendothelial pathways. Methods : Using shell-less cultures of 6-day-old chick embryos, efflux of fluorescein isothiocyanate (FITC)-dextran 150 from CAM microvessels was evaluated, after applications of compound 48/80 or exogenous histamine, by computer-assisted videodensitometric analyses. Real-time confocal imaging enabled optical differentiation of first-order pre- and postcapillaries from the capillary networks. Cytologic ultrastructure of the microvascular units was also evaluated. Results : Although endogenous histamine was measurable and its concentration was increased after application of compound 48/80, segmental endothelia of the CAM microvascular units consistently restricted extravasation of FITC-dextran 150. Furthermore, intravascular injections of histamine also failed to induce interendothelial gap formation or macromolecular flux across the segmental CAM endothelia. Conclusions : These results are consistent with the interpretation that histamine-activated transendothelial pathways are inactive in the CAM at day 6. Whether such inactivity serves to retard facilitation of CAM angiogenesis by activated mast cells remains to be tested.     

N-Acetylcysteine Antagonizes the Development But Does Not Reverse ACTH-Induced Hypertension in the Rat

We investigated the effect of antioxidant N-acetylcysteine (NAC) on adrenocorticotropic hormone (ACTH)-hypertension. Male Sprague-Dawley rats received NAC (10 mg/L) or water 4 days before ACTH/saline treatment for 13 days (prevention study). In a reversal study, NAC commenced on day 8 of ACTH/saline treatment and continued for 5 days. ACTH increased systolic blood pressure (SBP) in water drinking rats (111 ± 1 to 131 ± 3 mmHg, p < 0.001). In the prevention study, NAC + ACTH increased SBP (108 ± 2 to 120 ± 2 mmHg, p < 0.001) but less than ACTH alone (p′ < 0.05). In the reversal study, NAC had no significant effect (132 ± 4 to 124 ± 3 mmHg, ns). Thus, NAC partially prevented but did not reverse ACTH-induced hypertension.     

Estrogen Receptor Beta Does Not Influence Ischemic Tolerance in the Aged Female Rat Heart

Introduction: Ischemic heart disease remains the leading cause of morbidity and mortality in aged women, with a 2‐ to 3‐fold increase in incidence following menopause. Clinical trials have failed to demonstrate cardioprotective benefit from chronic estrogen (E₂) replacement therapy, yet protective effects of E₂ have been demonstrated in adult animal models and are mediated by the estrogen receptor (ER) subtypes ERα and ERβ. Aims: The aim of this study was to determine the effects of acute ERβ activation on ischemia/reperfusion (I/R) injury in adult, aged, and aged E₂‐deficient female rats. Methods: Hearts were isolated from adult (6 months; n = 9), aged (24 months; n = 13), and aged ovariectomized (OVX; n = 14) female Fischer 344 rats and subjected to 47 min of global I and 60 min of R. Rats were acutely treated with the ERβ‐agonist diarylpropionitrile (DPN; 5μg/kg) or vehicle 45 min prior to I/R; ERβ mRNA and protein levels were also assessed. Results: Acute treatment with DPN had no effect on functional recovery following I/R injury in adult, aged, or aged OVX female rats. Additionally, we were unable to detect ERβ mRNA or protein in the adult or aged female rat myocardium. Conclusions: Here, for the first time, our data suggest that acute ERβ activation does not impact ischemic tolerance in the adult or aged female Fischer 344 rat myocardium and this likely due to a lack of detectable ERβ.     

Biomarkers in Various Types of Atrophic Gastritis and Their Diagnostic Usefulness

Atrophic gastritis has been shown to involve either the oxyntic gland area, resulting in hypergastrinemia and hypopepsinogenemia I, the antral gland area, causing hypogastrinemia without change in serum pepsinogen I (diffuse antral gastritis; DAG), or the entire gastric mucosa (multifocal atrophic gastritis; MAG), resulting in both hypogastrinemia and hypopepsinogenemia I; and rare atrophic gastritis limited to the oxyntic gland area, with antibodies against oxyntic cells and/or intrinsic factor (autoimmune metaplastic atrophic gastritis; AMAG). This study was performed on 126 patients with various forms of gastritis and on 126 age- and gender-matched controls, who were subjected to endoscopy with biopsy, H. pylori testing (¹³C-UBT, serology), assays for serum gastrin and pepsinogen I, and testing for basal and pentagastrin-induced gastric acid secretion. The following groups of patients were examined: group I (N = 22), with AMAG; group II (N = 53), with DAG; group III (N = 51), with MAG; and group IV (N = 126), age- and gender-matched controls without gastritis. The following changes were found. In group I very high serum gastrin and very low pepsinogen I were observed, and all patients were achlorhydric and H. pylori negative. In group II, with low serum gastrin and normal pepsinogenemia and gastric chlorhydria, all patients were H. pylori positive. In group III, with lower serum gastrin and lower pepsinogen I levels and reduced chlorhydria, all patients were also H. pylori positive. And all group IV controls, with normal serum gastrin and pepsinogen I and normal gastric acid secretion without antral or fundic gastritis, were H. pylori negative. We conclude that measurements of serum gastrin and pepsinogen I and gastric acid secretion as well as testing for H. pylori infection may be useful in noninvasive diagnosis of various types of atrophic gastritis and in identification of patients with premalignant gastritis and a high risk of gastric cancerogenesis.     

Comparison of cAMP System in Parietal Cells from Rat and Guinea Pig

Adenylyl cyclase activity, cAMP content, and activation of cAMP-dependent protein kinase were measured in rat and guinea pig parietal cells isolated by the same procedure. Incubation of parietal cells with histamine resulted in aminopyrine uptake, stimulation of adenylyl cyclase activity, accumulation of intracellular cAMP, and activation of cAMP-dependent protein kinase. In addition, aminopyrine uptake and the cAMP system were stimulated in rat cells by epinephrine, whereas guinea pig cells were unresponsive to epinephrine. It is suggested that there may be differences between the two species with regard to receptors on the parietal cells.     

Identity of the Basally Located Parietal and Enterochromaffin-like Cells of the Rat Gastric Mucosa

When the argentaffin reaction for the glutaraldehyde- and osmium tetroxidefixed, epoxy-embedded sections was applied, two types of parietal cells were found in the glandular part of the rat gastric mucosa. The basally located ones were strongly argentaffin, whereas the superfical ones exhibited no such reaction. The argentaffin parietal cells at the bottom of the gastric glands showed a size, shape, intraglandular and intramucosal distribution similar to those of the cells taking up and storing exogenous 1-DOPA. It was concluded that the ‘enterochromaffin-like’ cells of the rat gastric mucosa are basally located parietal cells and that these parietal cells take up exogenously administered precursors of catecholamines and apparently store histamine.     

Biochemical Analysis of the Stomach Wall in Normal Rats

The rat stomach wall was analysed biochemically. The biochemical extraction was carried out according to the Schneider, Schmidt-Thannhauser's method. Acid-soluble inorganic phosphate, acid-soluble organic phosphate, phospholipid phosphate, ribonucleic acidic phosphate, deoxyribonucleic acidic phosphate, phosphoproteid inorganic phosphate were measured colorimetrically according to Briggs's method. The nucleic acids were estimated by measuring the phosphate and sugar components. The biochemical analysis was made both from the total stomach, and also separately from glandular stomach and the rumen. It is concluded that these two parts of the rat's stomach differ biochemically.     

The Effects of Hydrocortisone and ACTH on the Gastric Mucosa of the Rat

The effects of administering hydrocortisone (4 mg and 8 mg daily for 22 days) and ACTH (4 units and 8 units daily for 36 days) on the gastric mucosa of rats were assessed from the changes observed in the weight of the whole stomach, the surface area of the fundus, the height and volume of the fundic mucosa and the total parietal cell population. Both treatments reduced stomach weight and the height and volume of the fundic mucosa but the surface area of the fundus and the parietal cell population were not affected; no gastric ulcers were observed.

The results suggest that the administration of large amounts of the adrenocortical hormones inhibits the overall growth of the gastric mucosa.     

Studies on a Gastric inhibitory Substance Isolated from Juice of the Gastric Antrum in the Dog

Six mongrel dogs were prepared with vagally denervated antral pouches and Heidenhain fundic poucnes. An extract was prepared from juice secreted by the antrum by dialyzing against water and lyophilization. This gastric inhibitory substance (GIS) was assayed in the dog from which it was prepared. Three types of gastric secretion were studied: histamine-stimulated (50-200 µg per hour i.v.), gastrin-stimulated (1-3 mg per hour i.v.), and the response to a test meal consisting of 200 g strained beef liver homogenate. GIS injected in doses of I mg/kg body weight in a single i.v. dose reduced gastric acid secretion by 50-75 per cent. The gastric secretion of pepsin was not significantly altered by the injection of GIS. No severe side reactions were observed after the injection of GIS, except an elevation of body temperature. However, the relation between body temperature and inhibition was probably different from that encountered by others utilizing bacterial pyrogen.