Ultrastructural changes of the canine gastric mucosa after topical application of graded concentrations of ethanol

Curcuma aromatica Water Extract Attenuates Ethanol-Induced Gastritis via Enhancement of Antioxidant Status

Curcuma aromatica is an herbal medicine and traditionally used for the treatment of various diseases in Asia. We investigated the effects of C. aromatica water extract (CAW) in the stomach of rats with ethanol-induced gastritis. Gastritis was induced in rats by intragastric administration of 5 mL/kg body weight of absolute ethanol. The CAW groups were given 250 or 500 mg of extract/kg 2 h before administration of ethanol, respectively. To determine the antioxidant effects of CAW, we determined the level of lipid peroxidation, the level of reduced glutathione (GSH), the activities of catalase, degree of inflammation, and mucus production in the stomach. CAW reduced ethanol-induced inflammation and loss of epithelial cells and increased the mucus production in the stomach. CAW reduced the increase in lipid peroxidation associated with ethanol-induced gastritis (250 and 500 mg/kg, p < 0.01, resp.) and increased mucosal GSH content (500 mg/kg, p < 0.01) and the activity of catalase (250 and 500 mg/kg, p < 0.01, resp.). CAW increased the production of prostaglandin E₂. These findings suggest that CAW protects against ethanol-induced gastric mucosa injury by increasing antioxidant status. We suggest that CAW could be developed for the treatment of gastritis induced by alcohol.

Protective effects of DIDS against ethanol-induced gastric mucosal injury in rats

The compound 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) is an efficient anion exchanger inhibitor that can block the activities of anion exchanger 2 (AE2), which plays an indispensable role in gastric acid secretion. DIDS also has potent anti-oxidative and antiapoptosis activities. This study aimed to investigate the effect of DIDS on ethanol-induced mucosal damage in rats and to evaluate the underlying mechanisms that mediate the action of the compound. The rats received 1 ml of absolute ethanol or saline orally. DIDS [50 mg/kg intravenous (i.v.)] was given 5 min before ethanol administration. Gastric lesions were evaluated macroscopically, microscopically, and electron microscopically at 60 min after ethanol challenge. Gastric myeloperoxidase (MPO) activity, malonyldialdehyde (MDA) level, prostaglandin E2 (PGE2) synthesis, and cyclooxygenase-2 (COX-2) expression were assessed. For the evaluation of the effect of DIDS on gastric acid secretion, histamine-stimulatory gastric acid secretion was examined with or without pretreatment of DIDS (50 mg/kg; i.v.). Ethanol-induced gastric lesions were characterized by increasing gastric MDA level, MPO activity, and COX-2 expression, and decreasing PGE2 synthesis. It was found that DIDS significantly reduced the extent of gastric mucosal damage and reversed tissue MDA level and MPO activity. DIDS further enhanced the expression of COX-2 and reversed the decrease of PGE2. Our results suggested that DIDS is beneficial in rat model of gastric injury through mechanisms that involve inhibiting inflammatory cell infiltration and lipid peroxidation and up-regulating the COX-2/PGE2 pathway.

Gastric protection by α-melanocyte-stimulating hormone against ethanol in rats: Involvement of somatostatin

The proopiomelanocortin-derived tridecapeptide alpha-melanocyte-stimulating hormone (alpha-MSH) is a neuropeptide that exerts broad anti-inflammatory actions in mammals. This study aimed to investigate the effect of alpha-MSH on ethanol-induced gastric ulcer in rats and to evaluate the involvement of endogenous somatostatin in the actions of the peptide. The rats received 1 mL 75% ethanol or saline orally. alpha-MSH was given (25 micro g/rat; i.p.) alone or following the somatostatin antagonist cyclo-(7-aminoheptanoyl-PH-E-d-Trp-Lys-THR) (10 microM/kg; i.p.) administration. Gastric lesions were scored macroscopically and microscopically following decapitation at 30 min after ethanol challenge. Gastric malondialdehyde (MDA) level, myeloperoxidase (MPO) activity and mast cell counts were assessed. Ethanol-induced gastric hemorrhagic lesions were characterized by increased gastric MDA level, MPO activity and mast cell counts. alpha-MSH treatment decreased the extent of tissue injury and reversed tissue MDA level, MPO activity and mast cell counts. The effect of the peptide on the severity of gastric lesions, MDA level and MPO activity was reversed by the somatostatin antagonist. In conclusion, alpha-MSH is beneficial in a rat model of gastric ulcer via mechanisms which partly involve the endogenous somatostatin.

A new in vitro model for ethanol-induced gastric mucosal damage

A new in vitro model for ethanol-induced gastric damage is described. The stomach was dissected from the rat, a polyethylene cannula introduced into the remnants of the esophagus, and the pyloric end tied off. With the cardiac and pyloric regions of the stomach secured by thread to a vertical glass rod or tube, the whole was suspended in an organ bath containing aerated Krebs solution. Fifteen minutes later, ethanol was introduced via the esophageal cannula. After an additional 60 min, the stomach was removed from the Krebs solution, opened along the mid line, and the lesions studied. Comparisons were made with a conventional in vivo model. Results show that the lesion number, length, and total lesion area obtained by the in vitro model were comparable to those obtained in the older in vivo model. Histopathologically, lesions induced by both models were also comparable. Clonazepam, a drug previously used in the in vivo model, was tested in this model. Results indicate that clonazpam protected against ethanol-induced gastric damage in vitro. The new model provides a method to study the action of drugs on the stomach alone and to exclude in indirect actions of drugs via other sites in the body.

A study of the antiulcer mechanisms of propranolol in rats

Although propranolol has been shown to protect against ethanol and stress ulceration, the antiulcer mechanisms are still unclear. The present study examined the antiulcer mechanisms of propranolol in three different types of ulceration induced respectively by ethanol (60%), indomethacin (30 mg/kg) and stress (cold-restraint). Propranolol pretreatment in the highest dose (10 mg/kg) given either intraperitoneally (i.p.) or orally (p.o.) prevented gastric mucosal damage in these three ulcer models. The three doses of the drug (2.5, 5 or 10 mg/kg) dose-dependently decreased systemic blood pressure which was accompanied by a reduction of gastric mucosal blood flow. These findings suggest that the protection was unrelated to an improvement of local circulation in the stomach. However, propranolol preserved the mucus levels in the three types of ulcer models. The beta-adrenoceptor blocker also increased the basal gastric mucosal potential difference. These findings indicate that propranolol strengthens the mucosal barrier by the preservation of mucosal mucus and enhancement of the mucosal integrity in the stomach.

Drugs acting at central benzodiazepine receptors attenuate ethanol-induced gastric lesions in rats

The characteristics of the receptors involved in the protective action of benzodiazepines against ethanol-induced gastric lesions were investigated by studying the effect of benzodiazepine ligands on such lesions in both intact and unilaterally vagotomized rats. Clonazepam [5-(2-chlorophenyl)-1,3-dihydro-7-nitro-2H-1,4-benzodiazepine-2-one] a specific central-type receptor agonist (0.625-2.5 mg/kg p.o. or i.p.) and CGS 9896 [2-(4-chlorophenyl)-2,5-dihydropyrazolo(4,3-c)quinoline-3(3H)-one] a non-sedative partial agonist with anxiolytic properties (2.5-10 mg/kg p.o.) significantly reduced the gastric damage induced by ethanol (10 ml/kg of a 50% solution v/v p.o.) in non-vagotomized rats but Ro 5-4864 [7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepine- 2 -one] a pure peripheral-type receptor agonist (5-20 mg/kg p.o.) failed to affect this damage. The protective action of clonazepam and CGS 9896 against ethanol-induced gastric lesions was blocked, dose dependently, by the central-type receptor antagonist, flumazenil [ethyl 8-fluoro-5,6-5-methyl-6-oxo-4H-imidazo(1,4)f1p4odiazepine-3-carbox ylate] (1.25-20 mg/kg i.p.). In the unilaterally vagotomized rat, ethanol produced lesions in the right (vagotomized) and the left (non-vagotomized) halves of the gastric mucosa to nearly the same extent, while clonazepam and CGS 9896 uniformly decreased the lesions in both halves. It is concluded that central-type benzodiazepine receptors located in the stomach, specifically those mediating the anxiolytic effect of benzodiazepines, are involved in the protective action of benzodiazepines against ethanol-induced gastric lesions.

Effect of cerulein hyperstimulation on the paracellular barrier of rat exocrine pancreas

BACKGROUND/AIMS

Cerulein-induced pancreatitis causes a rapid increase in pancreatic enzyme levels in serum and decreases in pancreatic duct secretion and interstitial edema. One mechanism to explain these early events is disruption of the actin tight junction paracellular seal of acinar and intralobular pancreatic duct cells.

METHODS

To examine the paracellular barrier of the proximal exocrine pancreas, rats were hyperstimulated with 5.0 micrograms.kg-1.h-1 of cerulein. Actin was visualized with rhodamine phalloidin and by electron microscopy and tight junctions were visualized with antibodies to the tight-junction protein ZO-1. Paracellular permeability was measured by movement of horseradish peroxidase from interstitium into duct or acinar lumens.

RESULTS

In controls, linear actin and ZO-1 staining occurred along the apical membrane of intralobular duct cells and extended to the apical pole of acinar cells. Hyperstimulation caused progressive disruption of the linear staining of f-actin and ZO-1. Actin disruption in duct cells was confirmed by electron microscopy. Horseradish peroxidase entered intralobular ducts and acinar lumens of hyperstimulated animals more frequently than those of controls.

CONCLUSIONS

The structure and function of the paracellular barrier of acinar and intralobular pancreatic duct cells are disrupted early during cerulein pancreatitis and may contribute to early clinical features.

Effect of acute ethanol treatment on epidermal growth factor receptor in the rat stomach

The present study investigated the effect of acute ethanol (ETOH) treatment on the epidermal growth factor (EGF) receptor in rat gastric mucosa using two different experimental models. In the in vitro experiments, gastric mucosal cells were incubated with 0, 0.05, 0.1, 0.25, and 0.5% ethanol in Dulbecco's modified Eagle's medium (DMEM) for 30 min and then used for the membrane preparation. The EGF receptor binding assay indicated that cells incubated in the presence of ethanol displayed a concentration-dependent increase (r = 0.85) in the 125I-EGF binding. The Western blot analysis using anti-EGF-receptor antibody revealed that ethanol in vitro caused reduction in the immunoreactivity of the major 170-kDa protein. There were also alterations in the minor protein bands (140, 120, and 50 kDa). In the in vivo experiments, rats that fasted overnight were given 1.0 ml of saline or ethanol (5, 10, or 15%) by gastric intubation 30 min before sacrifice. In comparison with the saline controls, ethanol treatment caused a decrease of the EGF receptor binding to the gastric mucosal membrane (saline: 5%: 10%; 15% ETOH, 1.46 +/- 0.18: 1.13 +/- 0.17: 1.27 +/- 0.19: 0.84 +/- 0.14, p < 0.02; mean +/- SEM, n = 9). Furthermore, the immunoblot analysis revealed concentration-dependent decrease in the intensity of the major 170-kDa protein with ethanol. The reduction in the EGF receptor binding and the impairment of the receptor protein might be due to the nonspecific damage of the gastric mucosal membrane by ethanol.

Effect of ethanol on rat gastric surfactant: a fluorescence polarization study

BACKGROUND

Gastric surfactant is believed to protect gastric mucosa by the hydrophobic properties of its phospholipidic component, which are reflected in the fluorescence polarization of a lipophylic fluorescent probe. The present study aimed to observe the consequences of intragastric administration of 40% ethanol on the physical properties of rat gastric surfactant.

METHODS

Fluorescence polarization studies and lipid composition of gastric mucosal surface scrapings were performed.

RESULTS

Time course experiments indicated that the ulcerogenic action of ethanol occurred along with a fluidization of the surface scrapings followed by secondary rigidification. The fluidizing effect of ethanol was related to modifications of the molecular dynamics of lipid structures. The rigidifying effect of ethanol was a result of an increase in the cholesterol-triglyceride and cholesterol-phospholipid ratios and an increase in the percent composition of phosphatidyl-ethanolamine of surface scrapings.

CONCLUSIONS

The results suggest that alcohol could alter the gastric mucosal barrier by its disorganizing effect on the molecular dynamics of the gastric surfactant. The second rigidifying effect of ethanol could be a part of the damage repair phenomenon.

Ethanol-induced injury to the rat gastric mucosa. Role of neutrophils and xanthine oxidase-derived radicals

Ethanol-induced gastric mucosal injury closely resembles an inflammatory response. Thus, in vivo and in vitro experimental models were used to assess whether ethanol is proinflammatory in concentrations likely to be encountered by the gastric mucosa during acute intoxication. Perfusing the rat gastric lumen with progressively increasing concentrations of ethanol (10%, 20%, and 30%) resulted in a dose-dependent increase in 51Cr-ethylenediaminetetraacetic acid clearance from blood-to-gastric lumen. Rendering the animals neutropenic (with antineutrophil serum) ameliorated the ethanol-induced mucosal injury; the degree of protection was directly related to the severity of neutropenia. Neither superoxide dismutase, catalase, nor sodium benzoate offered any protection against ethanol-induced injury, indicating that neither superoxide anion, hydrogen peroxide, nor the hydroxyl radical is involved. To assess further whether ethanol could exert proinflammatory effects an in vitro model consisting of cultured bovine microvascular endothelial cells and isolated human neutrophils was used. Ethanol at concentrations of 1.0%-4.0% (but not at 0.1%-0.5%) increased neutrophil adherence to endothelial cells and enhanced neutrophil-mediated endothelial cell injury. We conclude that ethanol is proinflammatory at concentrations that may be achieved in the gastric mucosa during acute intoxication. The ethanol-induced, neutrophil-mediated cell injury does not appear to involve oxy radicals.

Evidence that adaptive cytoprotection in rats is not mediated by prostaglandins

We investigated the proposition that adaptive cytoprotection (enhanced gastric mucosal integrity) caused by exposure to 20% ethanol in rats is mediated by endogenous prostaglandin synthesis. Experiments were performed both without and with indomethacin sufficient to inhibit ex vivo release of prostaglandin E2 by 56% +/- 9% (2.5 mg/kg) or 86% +/- 4% (10 mg/kg). Twenty percent ethanol significantly reduced both macroscopic and histologic signs of injury caused by subsequent exposure to 100% ethanol whether or not the rats were pretreated with indomethacin. Twenty percent ethanol itself caused extensive superficial disruption of the surface epithelium, so that about half of the mucosa was covered by desquamated debris, but did not stimulate prostaglandin release. We conclude that adaptive cytoprotection still occurs after doses of indomethacin sufficient to cause a profound depression of prostaglandin E2 release. The possibility that it could be due to formation of a protective covering of surface debris is worth further investigation.

Studies on the mechanism of ethanol-induced gastric damage in rats

Concentrated ethanol causes gastric lesions by a mechanism that is poorly understood. We have investigated this mechanism in the rat stomach via gross morphologic, videomicroscopic, histochemical, and pharmacologic approaches. Within 1 min of contact, ethanol caused diffuse mucosal hyperemia. By 5 min, hyperemia greatly intensified at some mucosal sites. Beneath sites where mucosal hyperemia developed, intramural venules strongly constricted at 3-13 s postethanol, whereas submucosal arterioles dilated more than two times in diameter by 25 s. Submucosal venular constriction began sooner than arteriolar dilation (9 vs. 16 s, p less than 0.05). One-third of the gastric mucosal mast cells degranulated by 15 s postethanol; 50% discharged by 30 s. Ethanol-induced hyperemia was markedly reduced by lipoxygenase-selective inhibitors BW755C or nordihydroguaiaretic acid, or by the H1-antihistamine pyrilamine, but not by indomethacin, cimetidine, phentolamine, or methysergide. Based on these results, a model for the pathogenesis of ethanol-induced gastric lesions is proposed.

Ethanol-induced cell damage in cultured rat antral mucosa assessed by chromium-51 release

We have developed an in vitro method for studying ethanol-induced injury to gastric mucosa using organ culture of rat antrum. Cell damage was assessed by measurement of the release of [51Cr]sodium chromate from preloaded cells, a method adapted from a standard immunologic technique. This system provided rapid and highly reproducible quantitation of tissue injury as assessed by 51Cr release into the culture medium. The threshold concentration for ethanol-induced damage was between 10 and 15% v/v, similar to in vivo thresholds observed by others. 51Cr release could also be induced by very short exposure to ethanol (5-15 min), and then continued despite ethanol removal. Interestingly, after continuous ethanol exposure, a plateau of maximum 51Cr release was reached 60 min after exposure to ethanol over the concentration range 20-50%, suggesting tissue adaptation to ethanol damage. This organ culture system, which allows precise control of experimental conditions, may be useful for studying mechanisms of gastric mucosal injury and protection.

Ethanol, its effect on the synthesis of proteins by guinea-pig gastric mucosa

Incorporation of L-[U-14C]leucine into proteins is taken to indicate the synthesis of proteins by guinea pig gastric mucosa. Ethanol reduced the synthesis of proteins in vitro by homogenized mucosa, by isolated gastric epithelial cell preparations and by intact tissue. Intact stomach wall incubated without ethanol in phosphate buffered saline showed progressively increasing incorporation of the precursor into tissue proteins and into proteins which were secreted into the mucosal incubation media. On isopycnic CsCl gradient fractionation radioactive tissue proteins were found at the top of the gradient (fraction L1, sp.gr.1.11-1.20) while radioactive secreted proteins sedimented to the bottom of the gradient as the carbohydrate rich high density gastric mucosal glycoprotein fraction L3 (sp.gr.1.29-1.33). Ethanol significantly but reversibly reduced the incorporation of radioactive leucine by intact mucosa into both the tissue proteins and the secreted proteins. Uptake of the precursor into the intracellular acid soluble pool was not impaired by ethanol and no significant differences were detected in the specific activities of free intracellular leucine between the ethanol treated samples and the corresponding controls. It is suggested that the ulcerogenic nature of ethanol may be associated with inhibition of the synthesis of proteins within mucosal epithelium leading to reduction in the output of mucosal secretory glycoproteins with subsequent impairment of the cytoprotective properties of the dynamic mucous barrier.

Morphine enhances gastric mucus synthesis in rats

The effect of morphine on gastric mucus synthesis was studied in conscious rats, using the method of staining mucus with alcian blue then destaining it with magnesium chloride. It was found that morphine significantly enhanced gastric mucus synthesis, as did fentanyl, a non-histamine-liberating opioid. The effects of the opioids on mucus synthesis were significantly attenuated by pretreatment with naloxone 8 mg/kg or cimetidine 100 mg/kg. Cimetidine itself significantly suppressed gastric mucus production in saline-treated rats. These findings suggest that the increased gastric mucus synthesis caused by morphine is due to activation of opiate receptors and not to histamine release. It appears that cimetidine may counteract rather than block the receptor effects of the opioids by a direct action on the mucus-secreting glands.

Adherent and soluble mucus in the stomach and duodenum

Gastroduodenal mucus is present as a water insoluble gel adherent to the mucosal surface and as a viscous mobile solution in the lumen. The protective properties of the mucus against acid (with bicarbonate), pepsin (diffusion barrier) and mechanical damage depend on the quality (structure) and quantity (thickness) of the adherent mucus gel layer. Adherent mucus is a viscoelastic gel which is 95% (v/v) water. It is permeable to ions and smaller molecules (Mr c. 1000), but is impermeable to large proteins (Mr c. 17,000) including pepsins. However, mucus is solubilized rapidly by pepsin, more slowly (greater than or equal to 1 h) by thiol agents, and is unchanged following exposure to bile, acid and ethanol (less than 40%). Glycoprotein macromolecules (Mr greater than or equal to 2 X 10(6] are the structural components of the mucus gel and have a polymeric structure of glycoprotein subunits (Mr c. 5 X 10(5), for gastric mucus) joined by disulphide bridges between their protein cores. This glycoprotein polymerization, which is essential for gel formation and hence function, is the site of action of proteolytic enzymes and thiol agents. The glycoprotein polymeric structure is deficient in antral mucus from patients with peptic ulcer disease. In vivo, adherent mucus forms a thin but continuous cover of variable thickness (50-450 micron in man, about two-fold less in rat) over the gastroduodenal mucosa. Pepsin in gastric juice will rapidly dissolve this mucus cover and can be active up to luminal pH values of 5.(ABSTRACT TRUNCATED AT 250 WORDS)

The synthesis and secretion of gastric mucus glycoprotein by mucosal cells cultured in the presence of ethanol

The effect of ethanol on the synthesis and secretion of mucus glycoprotein in gastric mucosal cells was investigated. The mucosal cell suspensions were subjected to a short-term (4 h) culture in the presence of 0-1.5 M ethanol, with [3H]proline and [3H]palmitic acid as markers for glycoprotein synthesis and acylation. The synthesized labeled mucus glycoprotein was isolated from the incubation medium (extracellular glycoprotein) and from the mucosal cells (intracellular glycoprotein), and analyzed. Depending upon the ethanol concentration in the cell culture medium, two distinct effects on the synthesis and secretion of mucus glycoprotein were observed. The cells cultured in the presence of 0.02-0.1 M ethanol showed increased ability for the incorporation of [3H]proline and [3H]palmitic acid, and for the secretion of the newly assembled mucus glycoprotein. The synthesis of the glycoprotein increased 18-fold, acylation 5-fold, and secretion 10-fold. The synthesized glycoprotein, however, contained four to five times less of acyl-bound fatty acids. Ethanol at 0.1-1.5 M caused a marked reduction (62-64%) in the mucus glycoprotein synthesis, but the amount of glycoprotein released to the medium remained constant. This indicated that higher concentrations of ethanol caused the release of the preformed intracellular mucus glycoprotein reserves. The results demonstrate that gastric mucosal cells incubated in the presence of ethanol exhibit impaired synthesis and secretion of mucus glycoprotein, and that the severity of impairment depends upon the ethanol concentration.

Morphology of rat gastric mucosal damage, defense, and restitution in the presence of luminal ethanol

The morphology of ligated rat stomachs filled with absolute ethanol for 1, 7, 15, 30, and 60 min was studied. With interrupted blood circulation, the entire mucosa was destroyed within minutes. With intact circulation, the mucosae remained macroscopically normal or developed visible lesions. Areas with lesions had extensive surface and gland cell disruption and were hemorrhagic and hyperemic. Histologically, nonlesion sites had about 92% of the mucous cells on the surface and upper gastric pits destroyed within 1 min. Detached necrotic cells and an accumulation of an exudate with fibrin fibers formed a thick layer over the damaged mucosal surface. Intact cells from the gastric pits started migrating over the denuded basal lamina and after 7 min about 4% of the surface was reepithelialized. Within the next 8 min there was a sharp increase in mucosal restitution to about 54%. After 30 min 84% of the mucosa was restituted and there was only a slight increase to about 87% after 1 h of continuous exposure to ethanol. After 30 min the ethanol was diluted to about 40% vol/vol. Focal geyserlike eruptions of plasma containing polymerized fibrin were visible at sites of epithelial discontinuity. Restitution of the mucosal surface in the presence of luminal ethanol may be facilitated by the favorable microenvironment created by the thick unstirred layer formed by the mucoid coat of necrotic cells, fibrin, and continued plasma shedding.

Protection of rat gastric mucosa against ethanol injury by the new synthetic prostaglandin MDL 646

Oral administration to fasted rats of absolute ethanol produces extensive necrotic lesions of gastric mucosa as well as a massive leakage of proteins and mucus glycoproteins into gastric lumen. When the new synthetic prostaglandin MDL 646, belonging to the PGE1 series, is administered intragastrically (2 or 10 micrograms/kg) 30 min before ethanol administration, a significant protection of rat gastric mucosa against alcohol injury is observed.

Alcohol and the gastrointestinal tract

The effects of acute and chronic ethanol ingestion on esophageal motility and the potential complications of these alterations are reviewed. Injury to the gastric mucosa and the small intestine and alterations in intestinal absorption can also result from alcohol abuse.

The roles of ethanol and of acid in the production of gastric mucosal erosions in rats

This study was undertaken to differentiate between the morphological changes produced in chambered rat gastric mucosae by 40% ethanol and by 50 mM HCl. 40% ethanol produced both focal mucosal hyperemia and widespread exfoliation of the surface epithelium. Massive release of mucus accompanied both events. In the absence of acid the released mucus was stabilized by a network of fibrin, and epithelial continuity was re-established over non-hyperemic regions by migration of epithelial (and parietal) cells from the gastric pits. Hemorrhagic erosions occurred only in the presence of acid, but were limited to the hyperemic regions. Acid had the following effects: (1) platelet thrombi were destroyed, thus promoting hemorrhage; (2) destruction of the fibrin network by acid caused dissipation of the adherent mucous coat; (3) vulnerable cells which had previously shown only ischemic damage were irreversibly damaged by acid; (4) exposed basal lamina was destroyed, thus removing the substratum necessary for orderly epithelial re-establishment.

Gastric cytoprotection in man by prostaglandin E2

In healthy volunteers, the effects of topical prostaglandins E2 (PGE2), 1 mg, on transmucosal potential difference (PD), mucus secretion, and epithelial cell turnover were investigated. PGE2 increased gastric PD by 10 mV on an average and stimulated mucus secretion of the stomach by 50%. In contrast, epithelial cell turnover remained unchanged. Gastric output of H+ decreased, whereas the outputs of volume, Na+, and Cl- rose in response to PGE2, which effects would be compatible with increased secretion of bicarbonate. Topical administration of ethanol 40% (vol/vol) reduced PD by 25 mV (delta PDE) and enhanced epithelial cell shedding by 350% with concomitant discharge of mucus from stomach epithelium. Pretreatment of the stomach with 1 mg PGE2 prevented the ethanol-dependent epithelial cell exfoliation, indicating gastric mucosal cytoprotection. Delta PDE and discharge of mucus were not significantly altered by PGE2. We conclude that gastric cytoprotection by PGE2 in man might be mediated by stimulation of mucus and/or bicarbonate production.

Effect of ethanol on canine gastric epithelial ultrastructure and transmucosal potential difference

We correlated changes in the gastric transmucosal potential difference (PD), as an indicator of the integrity of the gastric mucosal barrier, with morphological evidence of injury in dogs which had received either intragastric saline or 5, 10, 15, or 30% ethanol. Increasing degrees of morphological damage were accompanied by greater, more rapid changes in PD. Furthermore, ultrastructural changes occurred within surface epithelial cells, not in the deeper parietal or zymogen cells, and initially did not involve disruption of the apical cell membrane. Typically, the tight junctions also were not affected, although in a minority of dogs small bleblike separations of the tight junctions were seen. We consider the gastric mucosal barrier to be represented morphologically by the interconnecting sheet of gastric epithelial cells and that ethanol breaks the barrier by first causing intracellular injury.

Observations on the gastric mucosa of rheumatic patients before and after ibuprofen administration as studied by the pentagastrin test, endoscopy, and light and electron microscopy

The initial results of a study set up to investigate the gastric mucosa in rheumatic patients receiving ibuprofen are described. The study involved seven male patients, aged between 17 to 70 years, suffering from various rheumatic diseases. All patients received a daily dose of 1200 mg of ibuprofen per os divided into three fractions and taken over periods of treatment ranging from one to six weeks. On the data obtained by the gastric secretion test, endoscopy, and specific histological and ultrastructure studies it is concluded that, in the cases investigated, ibuprofen could not be shown to be responsible for any significant modification of the gastric mucosa.