Rat Gastric Corpus Research Articles

Musashi-1 post-transcriptionally enhances phosphotyrosine-binding domain-containing m-Numb protein expression in regenerating gastric mucosa.

ObjectiveUpregulation of the RNA-binding protein Musashi-1 (Msi1) has been shown to occur in rat gastric corpus mucosa after ethanol-induced mucosal injury. However, there is no direct evidence linking Msi1 with gastric regeneration. We examined the process of tissue repair after acute gastric mucosal injury with Msi1-knock-out (KO) mice to clarify the role of Msi1 and Msi1-dependent regulation of m-Numb expression in regenerating gastric mucosa.MethodsAcute gastric injury was induced in Msi1-KO and wild-type ICR mice by administering absolute ethanol. Expression of the splicing variants of m-Numb mRNA and protein in the gastric mucosa were analyzed by quantitative RT-PCR and western blotting, respectively.ResultsWe demonstrated that phosphotyrosine-binding domain-containing m-Numb expression was significantly upregulated at both the mRNA and protein levels in wild-type mice at 3 h after ethanol-induced acute gastric injury. In contrast, in Msi1-KO mice, the m-Numb protein was expressed weakly, and was associated with delayed regeneration of the injured gastric mucosal epithelium. In the Msi1-KO mouse, the ratio of m-Numb mRNA to total m-Numb mRNA in the heavy polysome fractions was lower than that in the wild-type mouse. Further, we showed that m-Numb-enhancement in gastric mucous cells induced the expression of prostate stem cell antigen and metallothionein-2. Under the m-Numb enhancing condition, the gastric cells exhibited enhanced cell proliferation and were significantly more resistant to H2O2-induced cell death than control cells.ConclusionsMsi1-dependent post-transcriptional enhancement of m-Numb is crucial in gastric epithelial regeneration.

Exploration of Selective Gene Expression by Rat Gastric Corpus Epithelium

Exploration of Selective Gene Expression by Rat Gastric Corpus Epithelium

Selective gene expression by rat gastric corpus epithelium

The gastrointestinal (GI) tract is divided into several segments that have distinct functional properties, largely absorptive. The gastric corpus is the only segment thought of as largely secretory. Microarray hybridization of the gastric corpus mucosal epithelial cells was used to compare gene expression with other segments of the columnar GI tract followed by statistical data subtraction to identify genes selectively expressed by the rat gastric corpus mucosa. This provides a means of identifying less obvious specific functions of the corpus in addition to its secretion-related genes. For example, important properties found by this GI tract comparative transcriptome reflect the energy demand of acid secretion, a role in lipid metabolism, the large variety of resident neuroendocrine cells, responses to damaging agents and transcription factors defining differentiation of its epithelium. In terms of overlap of gastric corpus genes with the rest of the GI tract, the distal small bowel appears to express many of the gastric corpus genes in contrast to proximal small and large bowel. This differential map of gene expression by the gastric corpus epithelium will allow a more detailed description of major properties of the gastric corpus and may lead to the discovery of gastric corpus cell differentiation genes and those mis-regulated in gastric carcinomas.

Proton Pump Inhibitor-Induced Transepithelial Leak in Gastric Mucosa: Decrease of Leak with Long-Term PPI Use

Purpose: In previous patient-based studies our group has shown that proton pump inhibitors (PPIs) induce a transepithelial leak in gastric mucosa (Mullin, et al. 2008). This leak seemingly occurs without the onset of tissue inflammation or damage as assessed endoscopically. Using rat gastric corpus mucosa in Ussing chamber studies, we observed that PPI-induced leak is bidirectional and has a size limit of 10 kDa for solutes than can permeate through it (Murray, et al. 2009). We also observed that whereas the leak allows for charged as well as uncharged molecules to permeate, it exhibits a surprising degree of structural specificity in the types of molecules that can pass (Gabello, et al. 2009). Two small molecule drugs, digoxin and phenytoin, showed surprisingly different patterns, with digoxin able to permeate but phenytoin unable to permeate. We likewise observed that the small peptide bradykinin, can permeate, but the small peptide, oxytocin, cannot (Gabello, et al. 2010). Concerning kinetics, a (standard) 40 mg dose of esomeprazole is required for five days before a statistically significant leak is observed clinically. However, in rat gastric corpus Ussing chamber studies, exposure to 25 μM omeprazole results in instantaneous leak. The current study aimed to assess the long term effect of PPI use on transepithelial gastric leak. Methods: Subjects were enrolled with up to 20 years duration of PPI usage. To quantify transepithelial leak, subjects drank a concentrated sucrose solution followed by overnight collection of urine with subsequent measurement of sucrose concentration. Results: We observed that the PPI-induced leak effect decreases spontaneously in the first two years of PPI usage. Most of the decrease in leak is occurring in the first 10 months of PPI use. The phenomenon therefore exhibits tachyphyllaxis, self-correcting in the continued presence of the PPI. A linear regression of the sucrose leak in mg of sucrose vs. months on PPIs for 41 patients shows a declining slope (m=-0.8) with a y intercept of 220 mg and an r2 of 0.07. If the data are grouped as PPI use less than 3 months (n=11) and greater than 3 months (n=30) the mean values for leak are 330 mg and 130 mg respectively (P < 0.0003, Student's t). Conclusion: While PPI-induced trans-epithelial sucrose leak is present, it appears to decrease as a function of time. Most of this decrease occurs in the first 10 months of usage. Statistical significance of this decrease in leak was demonstrated based on whether patients had been taking PPIs for less than 3 months or greater than 3 months.

Differential distribution of ghrelin- O-acyltransferase (GOAT) immunoreactive cells in the mouse and rat gastric oxyntic mucosa

The enzyme that acylates ghrelin was recently identified in mice as the fourth member of the membrane-bound O-acyltransferases superfamily (MBOAT4) and named ghrelin- O-acyltransferase (GOAT). Only one report showed GOAT mRNA expression in ghrelin-expressing cells of the mouse stomach. We investigated the distribution of GOAT protein in peripheral tissues and co-expression with endocrine markers in the gastric mucosa using a custom-made anti-GOAT antibody. Tissues were collected from male Sprague–Dawley rats and C57BL/6 mice. Western blot revealed two immunoreactive bands in rat and mouse gastric corpus mucosal proteins, a 50 kDa band corresponding to the GOAT protein and a 100 kDa band likely corresponding to a dimer. Western blot also detected GOAT in the plasma and levels were strongly increased after 24-h fasting in mice and slightly in rats. GOAT-immunoreactive cells were located in the gastric corpus mucosa and the anterior pituitary gland, whereas other peripheral tissues of rats and mice examined were negative. In mice, GOAT-immunoreactive cells were mainly distributed throughout the middle portion of the oxyntic glands, whereas in rats they were localized mainly in the lower portion of the glands. Double labeling showed that 95 ± 1% of GOAT-immunoreactive cells in mice co-labeled with ghrelin, whereas in rats only 56 ± 4% of GOAT-positive cells showed co-expression of ghrelin. The remainder of the GOAT-immunopositive cells in rats co-expressed histidine decarboxylase (44 ± 3%). No co-localization was observed with somatostatin in rats or mice. These data suggest species differences between rats and mice in gastric GOAT expression perhaps resulting in a different role of the MBOAT4 enzyme in the rat stomach. Detection of GOAT in the plasma raises the possibility that ghrelin octanoylation may occur in the circulation and the fasting-induced increase in GOAT may contribute to the increase of acylated ghrelin after fasting.

Omeprazole Induces Gastric Permeability to Digoxin

Previous animal and patient-based studies have shown that omeprazole induces a transepithelial paracellular gastric leak. This study reports on the potential for an omeprazole-induced leak of drugs with narrow therapeutic windows. Ussing chamber experiments investigated the effects of omeprazole on rat gastric corpus permeability to the drugs, digoxin and phenytoin. Digoxin (780 MW) permeated the gastric mucosa at an accelerated rate in the presence of omeprazole. This leak could contribute to dangerous elevations of blood digoxin levels in certain situations. Omeprazole was found to have no effect on the flux rate of phenytoin (252 MW). The tight-junctional leak generated by omeprazole thus exhibits specificity to the types of molecules it allows to permeate through the gastric mucosa. This leak may pose a clinical danger by increasing drug uptake into the bloodstream, a phenomenon which would act synergistically with the effect of omeprazole on inhibiting liver cytochrome P450s that remove drugs from the bloodstream, thereby elevating drug blood levels.

Proton Pump Inhibitor-Induced Leak Across Gastric Mucosa: Effect of H-2 Blockers

Previous patient-based studies by our group have shown that the proton pump inhibitor, esomeprazole, induces a transmural leak in gastric mucosa (Mullin et al., Alimentary Pharmacology and Therapeutics, 28(11-12): 1317-25, 2008). Subsequent studies by our group using rat gastric corpus mucosa showed that this leak is bidirectional, has an upper size limit of 10 kDa, and is a class effect for PPIs in general, holding true for omeprazole and lansoprazole as well as esomeprazole. Additionally, we have demonstrated that the small molecule drug, digoxin, is capable of passing through this leak, with the potential of thereby elevating digoxin blood levels above their therapeutic target. In this current study we asked whether the H-2 blocker, famotidine, would have a similar effect to PPIs. Test subjects performed an initial (baseline) sucrose permeability test just prior to beginning medication. Subjects then took a daily (morning) dose of famotidine (40 mg) or omeprazole (20 mg) for 5 days. On the evening of the 5th (last) day, subjects performed a second sucrose permeability test. Subjects taking omeprazole for 5 days (n = 10) manifested a 5-fold increase in sucrose leak. Subjects taking famotidine for 5 days (n = 10) manifested only a 15% increase in leak, which was not statistically significant (P = 0.54, Student's t test). The increased leak of subjects on omeprazole was highly significant (P<0.0005). These findings support the hypothesis that induction of transmucosal gastric leak is not simply a function of inhibition of acid secretion, but instead is a property more specific to PPIs per se. Future studies will however test whether longer duration exposure to famotidine can induce leak, or whether a famotidine-induced leak disappears in 12-24 hrs after a 40 mg oral dose. This work was supported by funding from the Sharpe/Strumia Foundation.

Transmucosal Gastric Leak Induced by Proton Pump Inhibitors

Despite their remarkable safety profile and lack of clinical side effects, proton pump inhibitors (PPIs) induce a transmucosal gastric leak to non-electrolyte probes of various sizes. The ex vivo addition of PPIs to isolated rat gastric corpus increases transmucosal permeability in a dose-dependent manner, which corresponds with PPIs' dose-dependent inhibition of acid secretion. Upon the addition of omeprazole, lansoprazole, or esomeprazole, a small decrease in transepithelial resistance and the concomitant stimulation of short circuit current was observed. Additionally, transepithelial flux of (14)C-[D]-mannitol (MW 182.17) across the gastric mucosa increased by a mean of 68% immediately following the addition of 200 microM omeprazole. This flux increase was bidirectional. Omeprazole also increased the paracellular permeability to larger radiolabeled probes, including (14)C-sucrose (MW 342.3) and (14)C-polyethylene glycol (MW 4,000) by 118% and 350%, respectively. However, the flux of still larger probes, 10,000 and 70,000 MW dextrans, was not increased. Because PPIs are so widely used and are assumed to be innocuous, this transmucosal gastric leak must be further investigated, as it may carry considerable biomedical implications.

Calcium-independent tacrine-induced relaxation of rat gastric corpus smooth muscles

Tacrine, a non-competitive reversible acetylcholinesterase and butyrylcholineserase inhibitor, caused a concentration-dependent tonic contraction of gastric smooth muscle preparations in the concentration range 1 x 10(-7) mol/L - 1 x 10(-5) mol/L, whereas concentrations higher than 2 x 10(-5) mol/L induced a biphasic effect; a short-time contraction was followed by a prolonged relaxation. To shed some light on the mechanism underlying this untypical relaxation, the amplitude of mechanical reactions caused by tacrine were compared with those of tacrine in the presence of atropine, ipratropium, metrifonate, TTX, nifedipine, D-600, caffeine, apamin, and charybdotoxin. The results obtained revealed that the relaxation was neither cholinergic in nature, nor mediated by the influence of the drug on intramural neuronal structures. It was not influenced by processes inducing changes in cytosolic Ca2+ levels. This assumption was confirmed by experiments with permeabilized muscle preparations that were pre-contracted in a solution with pCa 5.5. Tacrine relaxed the smooth muscles in spite of the constant intracellular Ca2+ concentration resulting from the permeabilization. These findings argue that tacrine at concentrations higher than 2 x 10(-5) mol/L has a desensitizing effect on the contractile apparatus of gastric corpus smooth muscle preparations towards Ca2+.

Cell proliferation in the gastric epithelium of the ulcer rat

Objective. Cell division is brisk in the ulcer margin and many of the new cells will migrate over and cover the ulcer bed. The aim of this study was to determine how agents that promote or delay gastric ulcer healing influence cell proliferation in the gastric epithelium. Material and methods. Acetic acid ulcers were produced in the rat gastric corpus; non-ulcer rats served as controls. All rats were given a continuous infusion of 3H-thymidine. Some rats were also given gastrin or indomethacin, or infected with Helicobacter pylori. The rats were killed after 1, 2, 6 or 13 days, and the ulcer margin and undamaged corpus were excised for determination of labeling index (LI) by autoradiography. Antrum, duodenum and colon were also studied. Silver grain counting was carried out in some groups. Results. LI in the ulcer margin grew exponentially, reaching 84% after 6 days; gastrin increased, and indomethacin decreased LI significantly. In 6-day ulcer rats that were given 3H-thymidine only during the first day LI was 5%, while in those given 3H-thymidine only during the last day LI was 27%. LI and silver grain counting results indicated that during the first 6 days of healing the epithelial cells in the ulcer margin divide twice. In the undamaged epithelium of the 1-day ulcer rats LI was <one-third, and in the antral epithelium one-half of that in the non-ulcer controls. Conclusions. During the first 6 days of healing, the LI of the non-parietal epithelial cells increases exponentially in the ulcer margin; this is enhanced by gastrin. The unexpected finding in the ulcer rats of decreased LI in undamaged oxyntic and antral epithelium may be caused by a block of the G1 restriction point in the cell cycle. The reason for this remains obscure.

Parietal cell density during gastric ulcer healing in the rat

Background: During the healing of gastric ulcers, extensive changes take place in the structure and proportion of the parietal cells in the ulcer margin. We aimed to determine whether these changes are influenced by compounds or by procedures that may promote or delay gastric ulcer healing. Methods: Acetic acid ulcers were produced in the rat gastric corpus; control rats were non‐operated or sham‐operated. All rats were provided with an osmotic minipump releasing3H‐thymidine for determination of the labelling index (LI). The rats were given omeprazole, gastrin or indomethacin, infected with Helicobacter pylori, or subjected to anterior vagotomy. They were killed after 1, 2, 6 or 13 days, and the ulcer margin and undamaged corpus wall were excised for histology. The proportion of parietal cells was calculated in relation to the total number, and the total volume, of the epithelial cells. Results: The parietal cells averaged 16%–21% of the number and 30%–32% of the volume of the epithelial cells in the unoperated control rats, but considerably less in the ulcer margin. This reduction was partially prevented by indomethacin. In the undamaged, dorsal epithelium the parietal cells increased to 23%–26% of the number, and 41%–47% of the volume, of the epithelial cells, both in the ulcer rats and in the sham‐operated rats. The LI of the parietal cells was 6% in the undamaged epithelium of the 13‐day ulcer rats, but close to 0% in all other groups examined. Conclusion: Indomethacin prevents much of the loss of parietal cells in the ulcer margin. In the undamaged epithelium of the ulcer rats there is an increased proportion of parietal cells. The new parietal cells are not formed directly from dividing cells, but are probably recruited from existing precursor cells.

Influence of tacrine on dopamine-induced reactions of the gastric smooth muscle of rats

The clinical usage of the cholinesterase inhibitor tacrine for treatment of Alzheimer's disease is accompanied by adverse effects on the gastrointestinal tract. These adverse effects are a result of the direct action of tacrine on the intestinal smooth muscles or of the modulation of certain neurotransmitters regulating gastrointestinal functions. Dopamine is a neurotransmitter that modulates gastrointestinal motility. This study was designed to examine in vitro the effects of tacrine on dopamine-induced changes in spontaneous activity of smooth muscle preparations from rat's gastric corpus. The mechanical activity was isometrically registered. Tacrine 1.10(-7)-1.10(-5) mol/l caused smooth muscle contraction, which was blocked by atropine 1.10(-6) mol/l. Tacrine 1.10(-4) mol/l provoked a relaxation resistant to atropine. Dopamine and D(2)-receptor antagonists haloperidol and R121 had no effect on tacrine-induced relaxation. Dopamine-induced contraction was concentration-dependent. It was blocked by D(2)-receptor antagonists haloperidol and R121 and by tacrine 1.10(-4) mol/l. In the presence of tacrine 1.10(-7)-10(-5) mol/l or atropine the dopamine-induced contraction was significant. The data obtained suggested that tacrine 1.10(-4) mol/l inhibited the dopamine effects on gastric corpus smooth muscles. The effect was probably not dependent on its anticholinesterase activity or not realized through direct influence on D(2)-dopamine receptors.

Aspirin, and not rofecoxib, induces rapid up-regulation of iNOS and eNOS expression in the rat gastric corpus

Aspirin, and not rofecoxib, induces rapid up-regulation of iNOS and eNOS expression in the rat gastric corpus

Effect of roxatidine bismuth citrate (MX1) against acetylsalicylic acid- and indomethacin-induced gastric mucosal damage in rats.

We have studied the effect of the newly synthesized agent, roxatidine bismuth citrate (N-[3-(3-(1-piperidinyl-methyl)phenoxy)propyl]-hydroxyacetamide-2- hydroxypropane-1,2,3-tricarboxylate-bismuth(3+) complex), code name MX1, against acetylsalicylic acid (ASA)- and indomethacin-induced gastric mucosal damage in rats. Effects of MX1 (12.5, 50, 125, 184, 250 mg/kg) were compared to the effects of equimolar doses of roxatidine and bismuth subcitrate. Effect of MX1 (10(-6) M) on mucin biosynthesis measured by [3H] glucosamine incorporation in rat gastric corpus has been determined. MX1-pretreatment dose-dependently decreased the mean ulcer number and length in all doses used in an extent similar to that of roxatidine and more pronounced in comparison with bismuth subcitrate. The morphometrical results have been confirmed histomorphologically. The biosynthesis of mucin was found to be significantly enhanced after MX1 addition. The results of the present study suggest that MX1 has a gastroprotective effect against ASA- and indomethacin-induced ulcers which might be due both to its H2-blocking and mucus-stimulating activity.

Participation of nitric oxide in the relaxation of the rat gastric corpus.

Nitric oxide is an important mediator of the relaxation in the rat gastric fundus. The present study investigates the role of NO in the rat gastric corpus in vitro, since the corpus differs from the fundus with regard to its physiological function and its spontaneous motor behaviour. In the presence of guanethidine electrically induced relaxations of circular, mucosa-free corpus strips precontracted with bethanechol were concentration-dependently reduced by the NO-synthase inhibitors L-NG-nitro-arginine (L-NNA) or L-NG-nitro-arginine-methyl-ester (L-NAME). The D-enantiomers were markedly less active. The inhibitory effect of L-NAME could be prevented by L-arginine. L-NNA and L-NAME, however, did not influence spontaneous motility or the bethanechol-induced contraction. Vasoactive intestinal polypeptide or sodium nitroprusside also relaxed the muscle strips, but these relaxations were not affected by L-NAME. When the corpus strips were stimulated electrically from baseline, they reacted with a contraction followed by relaxation. L-NNA or L-NAME blocked the relaxatory and enhanced the contractile component. In strips that also reacted with a rebound contraction, it was blunted by L-NAME. These effects of the NO-synthase inhibitors were abolished in the presence of atropine. Apamin increased the electrically induced contraction of the muscle strips. Inhibition of the relaxation together with a further shift to contraction could only be seen when apamin was combined with L-NNA. The inhibitory action of apamin and apamin + L-NNA was not influenced by atropine. The results demonstrate a role of NO in the relaxation of the circular muscle of the rat gastric corpus both at a postsynaptic site and via inhibition of acetylcholine release. The relaxation induced by vasoactive intestinal polypeptide does not involve NO.

Expression and regulation of a vesicular monoamine transporter in rat stomach: a putative histamine transporter.

1. Vesicular monoamine transporters (VMATs) translocate monoamines from the cytoplasm into secretory vesicles of endocrine cells and neurones, but they have limited affinity for histamine, and the identity of the vesicular transporter for this monoamine is uncertain. The aims of the present study were to characterize VMAT representatives in rat gastric corpus, and to determine if their expression was regulated by factors that modulate histamine biosynthesis. 2. Polymerase chain reaction (PCR) cloning using oligonucleotide primers to DNA sequences conserved within the VMAT family provided evidence for VMAT2, but not VMAT1 in rat gastric corpus. Northern analysis using a VMAT2 complementary RNA probe revealed a single 4 kb mRNA species in corpus endocrine cells. 3. In rats treated for up to 5 days with the H(+)-K(+)-ATPase inhibitor omeprazole, VMAT2, histidine decarboxylase and chromogranin A mRNA abundance in gastric corpus, and plasma gastrin concentrations increased progressively. Omeprazole also elevated VMAT2 expression in rats fasted for 48 h, but fasting alone, or refeeding fasted animals had no effect. 4. The results are consistent with a role for VMAT2 in the transport of histamine into enterochromaffin-like cell secretory vesicles, and with upregulation of the transporter to accommodate the increased histamine biosynthesis and secretion that accompanies achlorhydria.

Differential expression and regulation of SSTR2 messenger RNA in rat gastric antrum and corpus.

Somatostatin modulates both endocrine and exocrine functions in the gastric mucosa, where three of the five cloned somatostatin receptors are present. This study examines changes in somatostatin receptor (SSTR) mRNA abundance during fasting, feeding, and profound acid inhibition with omeprazole. Serum gastrin as well as somatostatin and SSTR mRNA abundances were measured in antrum and corpus. In Northern blots of corpus RNA, the SSTR2 probe hybridized with two previously reported species of mRNA (2.4 and 2.8 kb); in addition, a weak previously unreported 1.6-kb band was detected. In antrum, the 1.6-kb band dominated. Fasting increased antral somatostatin mRNA from 100 +/- 8 to 161 +/- 24% and SSTR mRNA from 100 +/- 10 to 179 +/- 14% (P < 0.05). Omeprazole reduced antral somatostatin mRNA to 34 +/- 4% of control (P < 0.05) and elevated SSTR mRNA to 135 +/- 5% of control (P < 0.01). Omeprazole treatment reduced corpus somatostatin mRNA to 59 +/- 5% (P < 0.05), and elevated SSTR mRNA to 140 +/- 3% of control (P < 0.01). The results therefore indicate that a novel SSTR mRNA subtype exists in the stomach and predominates in the antrum. The abundance of this SSTR mRNA is upregulated by both fasting and achlorhydria; conditions that increase or decrease endogenous antral somatostatin, respectively.

Differential expression and regulation of somatostatin-receptor subtypes in rat gastric antrum and corpus : ∗R.Dimaline, A.K.Sandvik and E.Brenna. ∗Physiological Laboratory, University of Liverpool, and Department of Physiology, University Hospital, Trondheim, Norway

Differential expression and regulation of somatostatin-receptor subtypes in rat gastric antrum and corpus : ∗R.Dimaline, A.K.Sandvik and E.Brenna. ∗Physiological Laboratory, University of Liverpool, and Department of Physiology, University Hospital, Trondheim, Norway

Characterization of a vesicular monoamine transporter (VMAT 2) from rat gastric corpus, and upregulation by achlorhydria : [formula omitted], J. Struthers. Physiological Laboratory, University of Liverpool, Liverpool, UK

Characterization of a vesicular monoamine transporter (VMAT 2) from rat gastric corpus, and upregulation by achlorhydria : [formula omitted], J. Struthers. Physiological Laboratory, University of Liverpool, Liverpool, UK

Pharmacological evidence for the release of galanin from rat stomach

The neuropeptide galanin has been shown to occur in nerve fibres in the circular muscle layer of the rat stomach. The present experiments aimed at demonstrating a functional correlate for this observation by testing the motor effects of galanin on circular strips of the rat gastric corpus in vitro. Exogenous galanin elicited only small contractions of the smooth muscle which were dose-related but did not show a clear sigmoid dose-response relationship. These responses were resistant to atropine plus guanethidine or TTX. When the muscle strips were electrically stimulated, they showed pronounced rebound contractions after the end of the stimulus. These rebound contractions were significantly reduced by either desensitizing the strips to galanin or by addition of spantide. It is concluded that galanin is released from the myenteric plexus in the stomach and acts to modulate gastric contractions either postsynaptically or by modifying the release of tachykinins.