Adaptation of the gastric mucosa to repeated administration of aspirin in the rat

The effects of single and repeated doses of aspirin on the gastric mucosa of the rat were compared to determine whether the mucosal response alters after repeated aspirin. Aspirin (120 mg/kg) was administered by esophageal intubation either as a single dose or daily for 3, 14, 28 and 56 days. Mucosal damage was present in all treated rats but, on histologic quantitation, there was a highly significant reduction in the numbers of acute erosions in the groups receiving repeated daily aspirin. This apparent adaptation did not persist when aspirin administration was interrupted for 3 days. Repeated aspirin administration was not associated with any reduction in aspirin absorption or excretion, nor was there any significant change in hydrochloric acid or pepsin secretion. The investigation has shown an adaptation to repeated aspirin in the rat which appears to result from an alteration in the gastric mucosa. The precise mechanism of the adaptation remains uncertain.Supported by the National Health and Medical Research Council and the Alfred Hospital.Presented, in part, to the Gastroenterological Society of Australia, May 1971.     

Healing of cysteamine-induced duodenal ulcers in the rat

The mechanism and time for healing of cysteamine-induced duodenal ulcers in rats were investigated. Cysteamine induces a mixture of erosions, ulcers, and penetrating ulcers. These three stages of ulcerations healed in different ways and in different times. Erosions healed within three days by formation of new mucosa from the epithelium of the remaining parts of the crypts of Lieberkühn. The mucosa became completely normal within 15 days. Ulcers healed primarily by a contraction of the circular layer of the external muscle coat, thereby approaching the ulcer edges and reestablishing a complete layer of Brunner's glands in the submucosa. Healing was complete within 15 days. Penetrated ulcers healed very slowly by formation of new epithelium and Brunner's glands from the ulcer edges. The newly formed epithelium was desquamated unless protected by underlying Brunner's glands and the regeneration of these therefore determined the healing of the ulcer. Only a few of these ulcers had healed after 50 days. After 100 and 150 days, approximately 50% had healed, and after 200 days still only 64% had healed. Thus the cysteamine ulcer with destroyed muscle coat has a very prolonged healing and thereby represents a model for a chronic duodenal ulcer which may be of value as a model for testing treatments of duodenal ulcers.     

A possible defensive mechanism in the basal region of gastric mucosa and the healing of erosions

A possible defensive mechanism in the basal region of the gastric mucosa was hypothesized in the present study. In vivo microscopy was performed to observe the basal region after thermal injury to the back skin of rats. A donor of nitric oxide, 3-morpholinosydnonimine hydrochloride (SIN-1), or a serine protease inhibitor, camostat mesilate, was administered. Anti-vascular endothelial growth factor (VEGF) neutralizing antibody was administered 5 hours after thermal injury (anti-VEGF group). Post-capillary venules could be observed in the basal region of the gastric mucosa (PV-BGM). The PV-BGM was dilated 5 hours after thermal injury, and it was reduced by the administration of SIN-1 or pre-treatment with camostat mesilate. In the control group, the erosions did not reach the basal region of the gastric mucosa. Most of the erosions healed within 72 hours. Delayed healing was observed in the anti-VEGF group. In this group, exudation and congestion in the basal region were observed at 24 hours, and ulcer formation was observed at 72 hours after thermal injury. It is thus hypothesized that blood flow of the PV-BGM increases when superficial mucosal circulation is disturbed. The PV-BGM can contribute to defensive mechanisms in the basal region of gastric mucosa. The abnormal healing process may disturb the defensive mechanism at the base of the gastric mucosa, thereby resulting in ulcer formation.     

Gastric adaptation occurs with aspirin administration in man

Endoscopy has become a standard method to evaluate drug-induced damage to the gastroduodenal mucosa; however, studies defining the time course, extent, and duration of the injury in man are unavailable. We report a systematic endoscopic evaluation of the effect of aspirin administration on the gastric mucosa in normal volunteers. Aspirin (2.6 g/ day) or placebo was administered for 1 or 7 days. Gastroscopy was performed after 1, 2, 4, and 8 days, and every other day thereafter until the lesions resolved. Submocosal hemorrhages and/or focal erosions were present within 24 hr in all subjects. With continuous aspirin administration, injury was maximal within 3 days and then lessened, ie, damage present after 7 days of aspirin was significantly less than after 1 day of therapy. The time to resolution of the damage was also longer following 1 day than after 7 days of aspirin (median 8 days for 1 day of aspirin vs median 3 days for 7 days of aspirin). Thus, gastric mucosal adaptation occurred and was associated both with less damage and with an accelerated healing process. Acute administration of aspirin produced well-defined areas of submucosal hemorrhages within 2 hr of administration; additional doses increased the area of involvement but not necessarily the severity of involvement.     

Resistance to medical therapy of gastric ulcers in rheumatic disease patients taking aspirin

Little is known about healing or recurrence of aspirin-induced gastric ulcers if aspirin intake is continued. A double-blind controlled study compared cimetidine plus antacids as needed (prn) with placebo plus prn antacids in healing aspirin-associated gastric ulcers during continued salicylate ingestion in 18 rheumatic disease patients over a 2-month period. Healing occurred in 44% of the placebo and 56% of the cimetidine-treated patients (P>0.05). Subjects in both groups ingested potentially therapeutic doses of antacid. Ulcer size had an effect on healing rate, irrespective of treatment. Ninety percent of gastric ulcers<0.5 cm in diameter healed in 2 months but only 25% of ulcers>0.5 cm. Six of seven patients with unhealed ulcers at 2 months eventually healed medically at intervals of 6–26 months. Of 11 patients managed medically and followed endoscopically for a mean of 15 months after healing, only one had a recurrent ulcer. In conclusion, placebo and antacid therapy were as effective as cimetidine and antacids in healing ulcers over a 2-month period. In spite of continued aspirin intake, most benign gastric ulcers <0.5 cm in diameter heal medically in two months. Aspirin-induced ulcers1 cm in diameter are relatively resistant to therapy but can be healed with prolonged cimetidine and antacid treatment; once healed, recurrence rate is low with prophylactic therapy even with continued aspirin intake.This work was supported in part by the Medical Research Service of the Veterans Administration and by CRC NIH grant RR00287-12. Assistance of John Hewitt, PhD, biomedical statistician, is gratefully acknowledged. Data from this paper were presented in part at the annual meeting of the American Gastroenterological Association, Salt Lake City, Utah, May 1980.     

The role of aspirin in gastric ulceration

The gastric irritant effects of aspirin were studied in rats treated with a variety of physical and disease (inflammatory) stress conditions (which may mimic responses to some stress states encountered clinically with the object of establishing whether these stress states increase the susceptibility of the gastric mucosa to the potentially ulcerogenic actions of aspirin. While exposure to physical (eg, cold) stress conditions markedly increased the sensitivity of the gastric mucosa to aspirin, exposure to various disease stressors (eg, adjuvant arthritis, acute pain, or paw inflammation) did not appreciably affect the mucosal sensitivity to this drug. Attempts were made to determine the mechanisms of the physical stress plus aspirin interaction by use of pharmacological agents. The results suggest a major involvement of the parasympathetic-vagal, sympathetic, and histamineproducing systems, but not the adrenocortical axis, in this model of gastric ulcerogenesis. No differences were observed in the mucosal uptake of [¹⁴C]aspirin, showing that accelerated uptake of the drug is not a factor in the development of gastric ulceration.This study was financed by the National Health and Medical Research Council (Australia) and the University of Tasmania Research Committee.     

Experimental chronic gastric ulcer due to ischemia in rats

Ligation of the left gastric and right gastroepiploic arteries and veins resulted in chronic gastric ulcer formation in the rat. Linear mucosal corpus hemorrhages appeared within 8 hr of ligation. By 2 days large corpus hemorrhagic erosions were present. A single, large ulcer involving nearly the entire corpus was present at 3–5 days. In the ulcerated area the mucosa and muscularis mucosae were destroyed, thick granulation tissue filled the submucosa and the muscularis propria was severely damaged. Progressive healing occurred thereafter and 75% of the ulcers healed completely grossly in 2–8 weeks. Histologic studies showed that healing and mucosal regeneration occurred by the outgrowth of a layer of cells from the adjacent intact epithelium extending over the surface of the ulcer. Invaginations from this covering layer of cells formed a glandular mucosa composed of mucous cells. Later parietal and chief cells appeared, and eventually (6 months) a normal corpus-type mucosa covered the entire corpus. With time smooth-muscle fibers appeared in the outer half of the dense submucosal granulation tissue and eventually a normal muscularis mucosae, submucosa, and muscularis propria were present (6–12 months). These studies show that: (1) ischemia can give rise to chronic gastric ulcer, and (2) all elements of the gastric wall, including the mucosa, the muscularis mucosae, and the muscularis propria can fully regenerate.Supported by Veterans Administration Project Number 3324-02 and NIAMDD Peptic Ulcer Center Grant 17328     

Factors influencing healing of duodenal ulcer

To study the efficacy of a single bedtime dose of H₂-receptor antagonist in the healing of duodenal ulcer, a 12-week randomized double-blind controlled trial of oxmetidine, which is equipotent to cimetidine and has a similar duration of action, was performed in 80 patients. Oxmetidine, 600 mg bedtime, resulted in significantly more complete healing than placebo at weeks 2, 4, 6, 8, 10, and 12 as assessed endoscopically. At weeks 4 and 6, 72.5% and 85%, respectively, of ulcers were completely healed by oxmetidine, and 36.8% and 41.7%, respectively, by placebo. Of 45 prospectively obtained patient characteristics, high pentagastrin-stimulated maximal acid output and large ulcer diameter significantly affected healing adversely. These results indicate that duodenal ulcer healing may be achieved by reducing the nocturnal acid secretion alone.Part of work presented at American Gastroenterological Association Annual Meeting, May 23–25, 1983, Washington D. C. Supported by University Research Grants (041.0006, 041.0009) and Wing Lung Bank Medical Research Fund (311/030/8009/31), University of Hong Kong.     

Effects of misoprostol on delayed ulcer healing induced by aspirin

Clinical studies have suggested that treatment with the prostaglandin E₁ analog, misoprostol, leads to significant healing of ulcers in patients taking regular nonsteroidal antiinflammatory therapy. This study aimed to investigate mechanisms involved in this healing using a rat model. Gastric ulcers were induced by application of acetic acid using a standard technique. Rats were treated with 200 mg/kg aspirin, 100 µg/kg misoprostol, a combination of both treatments, or methylcellulose vehicle for up to two weeks, starting two days after ulcer induction. Ulcers were assessed by macroscopic measurements of area and by quantitative histological measurements. Aspirin delayed ulcer healing compared with controls, while misoprostol significantly reversed this effect. Quantitative histology revealed that misoprostol cotreatment significantly increased mucosal regeneration compared with aspirin treatment alone. However, misoprostol did not reverse the effects of aspirin on an index of wound contraction. We conclude that treatment with misoprostol significantly reverses the delayed healing effect of aspirin, and this may occur via an effect on epithelial regeneration.This study was supported by a grant from the Alfred Hospital Medical Research Advisory Committee.     

Mucosal and hepatic metabolism during the spontaneous disappearance of salicylate-induced gastric erosions

Salicylate-induced gastric erosions have been shown to disappear despite continuing salicylic acid administration in the rat. On the other hand, numerous drugs are able to change the capacity of the gastric mucosa to conjugate xenobiotics, which gives reason to follow gastric resistence to salicylic acid and to correlate it with changes in mucosal rate of drug biotransformation reactions. Gastric and duodenal UDP glucuronyltransferase activity decreased markedly within 12 hours after a single dose of salicylic acid. When continuing salicylic acid administration, macroscopic gastric lesions disappeared within 3 days and mucosal UDP glucuronyltransferase activity increased above control level. In 2 weeks the activity returned to control level. In spite of the fact that salicylates markedly inhibited gastroduodenal glucuronidationin vitro, there was no substrate effect of salicylic acid present at the time the rats were killed. Duodenal 3,4-benzpyrene hydroxylase activity was not affected by salicylic acid administration. The gastric activity of benzpyrene hydroxylase in controls and in rats treated with salicylic acid was below the sensitivity of the method. Hepatic detoxification capacity was quite stable. A slight depression of 3,4-benzpyrene hydroxylase activity did, however, take place within 2 weeks. Gastric and duodenal protein contents decreased after a single salicylic acid administration, but returned to control level in 5 days in the duodenum, and in 2 weeks in the stomach, when the administration was prolonged. The results suggest that mucosal detoxification capacity may have a role in the pathogenesis of drug-induced gastric erosions. Gastric mucosa adapts to repeated salicylic acid administration, having reduced susceptibility to drug-induced erosions.     

Indomethacin treatment during initial period of acetic acid-induced rat gastric ulcer healing promotes persistent polymorphonuclear cell-infiltration and increases future ulcer recurrence

The study was performed to examine whether indomethacin administered during the initial period of acetic acid-induced gastric ulcer healing affects future ulcer recurrence. Gastric ulcers were produced in rats by subserosal injection of acetic acid. Indomethacin (1 mg/kg/day, orally) administered either alone or concomitant with ornoprostil (50µg/kg/day, orally) was started on the fourth day and continued for 56 days. In rats whose ulcer healed at the 90th day after production of ulcer, endoscopy was done every 30 days to examine recurrence of ulcer. Gastric specimens were obtained 10, 30, 60, 90, and 240 days after ulcer production for histology, to quantitate the height of regenerated mucosa, thickness of fibrous tissue, degree of polymorphonuclear cell infiltration, and PAS-positive cells. Cumulative ulcer recurrence rate was significantly higher in rats initially treated with indomethacin than in controls. Increased polymorphonuclear cell infiltration was the major histologic abnormality persisting after cessation of indomethacin. Ornoprostil reversed these abnormalities caused by indomethacin. In conclusion, the administration of indomethacin during the initial period of the ulcer healing promoted persistent polymorphonuclear cell infiltration and increased ulcer recurrence rates, possibly via a prostaglandin-dependent mechanism.The work was supported by The Ministry of Education, Science and Culture of Grant-in-Aid for General Scientific Research 02454236 and by the DVA Medical Research Service.     

Stomach tolerance of various fluoride preparations. An endoscopy controlled single-blind study of healthy probands]

In 12 healthy volunteers the gastro-duodenal damaging effects of Ossiplex retard tid, Mono-Tridin tid and Ossin bid were investigated in a randomised, single blind cross-over study. Prior to the start of the three therapeutic phases subjects underwent endoscopic examination to exclude gastro-duodenal mucosa lesions. On day 14 of therapy 2 hours after the application of the last fluoride dose subjects underwent endoscopy again. The 14 days administration of Ossiplex retard, Mono-Tridin und Ossin led to gastro-duodenal mucosa lesion scores of 0.42 +/- 0.26; 1.50 +/- 0.54 and 2.08 +/- 0.71 (mean +/- SEM) respectively. These differences were statistically significant when comparing Ossiplex retard vs Ossin (p less than 0.05), but not Ossiplex retard vs Mono-Tridin. Regarding the number and the severity of lesions the differences between the gastro-duodenal mucosa damaging potency of the three fluoride preparations were also evident. With Ossiplex retard only in three subjects petechiae (n = 1) and antral erythemas (n = 2) were observed. Under Mono-Tridin and Ossin, however, a higher grade of lesions i.e. erosions and an ulcer were seen endoscopically. This study shows that the slow release fluoride preparation Ossiplex retard demonstrates a lower gastro-duodenal mucosa damaging potency when compared to the other fluorides Ossin and Mono-Tridin. There was no relationship between serum fluoride concentrations and the grade of gastro-duodenal mucosa lesions.     

Healing and relapse of reflux esophagitis during treatment with ranitidine

In 108 patients the healing and relapse of reflux esophagitis, defined endoscopically by the presence of epithelial defects (erosions and ulcerations) of the esophageal mucosa, were studied. In the first study, with open treatment of ranitidine, the healing rate after 6 wk was 50%. The most important factor that negatively influenced healing was the extent of esophageal erosions. Patients with isolated erosions had a 6-wk healing rate of 78%; the healing rate was 38% in patients with longitudinally confluent lesions and 23% in those with circumferential erosions of the distal esophagus. Smoking also had an unfavorable effect. Age, sex, duration of history, body weight, and alcohol consumption were not related to outcome. Symptoms improved during treatment with ranitidine, but the correlation between symptoms and endoscopic findings at 6 wk was weak. In the second study, relapse was investigated in 61 patients with healed esophagitis in a randomized, double-blind trial comparing placebo and ranitidine (150 mg at bedtime for 6 mo). In both groups, relapse occurred in more than one-third of the patients, with no significant difference between ranitidine and placebo treatment. Patients with worse daytime symptoms at the time of previous healing had a higher relapse rate. The initial severity of esophagitis and smoking did not influence recurrence. Thus, the initial endoscopic findings are of prognostic value in reflux esophagitis. Smoking retards healing. Low-dose maintenance treatment with ranitidine does not prevent relapse.     

Increased expression of epidermal growth factor receptor during gastric ulcer healing in rats.

Expression of epidermal growth factor receptor (EGFR) was studied immunohistochemically in rat gastric mucosa during healing of acetic acid-induced ulcers. In normal control gastric oxyntic mucosa, EGFR was expressed in proliferative zone cells and in some parietal cells. In mucosa of the ulcer margin, at 3, 7, and 16 days after ulcer induction, there was a 75-fold increase (over controls) in the number of cells expressing EGFR. Seventy percent of ulcers healed by the 16th day, and all were healed by the 25th day. The mucosal scar that replaced the ulcer was composed of dilated glands lined with poorly or aberrantly differentiated cells showing persistence of increased EGFR expression. An increased EGFR expression indicates an important role of EGF in ulcer healing and scar formation.     

Aspirin damage to ischemic gastric mucosa in shocked cats.

Cardiac output and blood flow to different regions and layers of the stomach were determined by the microsphere distribution technique. Aspirin tablets were placed in the stomach of anesthetized cats by gastrotomy. In some animals the arterial pressure was reduced to about 60 mmHg for 30 min by bleeding. The gastric mucosal blood flow decreased markedly during the bleeding. Three hours after reinfusion of the blood gastric mucosal erosions were present at the site of contact of the tablet with the mucosa. In most of the non-bled animals no mucosal lesions were found 4 1/2 after aspirin application. No mucosal damage occurred in animals subjected to bleeding without aspirin treatment. It is concluded that the aspirin damage to the gastric mucosa increases under hemorrhagic shock because of mucosal ischemia in the shocked animals.     

Alcohol injury to gastric mucosa in mice and its potentiation by stress

This investigation was initiated to separately evaluate the roles of dose and concentration of ethanol ingestion in the development of acute gastric mucosal injury and to determine the significance of stress as a potentiating factor in ethanol damage. A total of 423 mice were used in this study. Alcohol at the low concentration of 10% and at any of the doses used (1–5 g/kg wt) did not cause gastric mucosal lesions. Similarly, alcohol at the low dose of 1 g/kg wt at any of the concentrations used (10–50%) did not produce any gross injury to the stomach. A single oral administration of ethanol, given at doses of 2–5 g/kg wt and at concentrations of 25–50%, resulted in hyperemia and multiple fundic erosions and, less frequently, antral erosions. The incidence, number, and severity of these lesions rapidly increased with increase in ethanol concentration, ethanol dose, or both. Healing was rapid; at best, lesions were only barely visible 72 hours after alcohol ingestion. Repeated daily doses of ethanol given for 3–5 days did not increase the incidence and number of lesions, probably due to their capacity for rapid healing. Mild stress, in the form of 1-hour restraint in the cold room at 8°C, by itself caused very little mucosal injury in mice, but significantly potentiated the injurious effect of 35% ethanol administered in a 3 g/kg dose. Stress following alcohol intake potentiated gastric mucosal injury much more than if the stress preceded the alcohol ingestion. The incidence, number, and severity of erosions was here 3, 4 and 11 times, respectively, greater than the additive effect of alcohol and stress together (P<0.001). Thus, the extent of ethanol damage to the stomach related both to the concentration and dose of ethanol ingested. Stress, especially when following excessive ethanol intake, was a highly significant factor in the potentiation of acute alcoholic gastric mucosal injury.Supported by Grant-in-Aid AA-000312-1 from the Division on Alcoholism and Alcohol Abuse of the National Institute of Mental Health, Public Health Service.Dr. Kawashima was the recipient of a travel grant from the Natio Research Grant, Tokyo, Japan, for 1971.     

Healing process of duodenal ulcers induced by indomethacin plus histamine in rats

Healing of duodenal ulcers induced by indomethacin + histamine was investigated in rats. Animals were treated with indomethacin (5 mg/kg, s.c., once daily) and histamine (40 mg/kg, s.c., 3 times every 2.5 h after indomethacin treatment) for 2 days under fasting conditions, and they were fed normally thereafter. The duodenal ulcers so induced were confined to the proximal part of the duodenum and penetrated to the muscular mucosa with an incidence of over 80% when determined 32 h after the first injection of indomethacin (day 1). The ulcers became smaller and shallower within 7 days with granulation from the ulcer base, the mucosa grew in from the edges over the surface of granulation tissue, and they had healed almost completely after 15 days with epithelial regeneration from the edge of the ulcers. The healing of ulcers was significantly promoted by a 5-day treatment with an antacid (Al(OH)3) as well as antisecretory agents (omeprazole, cimetidine, propantheline bromide) and 16,16-dimethyl prostaglandin E2 at the dose which produced a potent inhibition of acid output and a marked increase in duodenal alkaline secretion. These results suggest that the duodenal ulcers induced in rats by indomethacin + histamine may provide a useful model for studying the healing process of duodenal ulcers and for the evaluation of the drugs with possible effects on ulcer healing.     

Effect of antisecretory agents and vagotomy on healing of “chronic” cysteamine-induced duodenal ulcers in rats

Penetrated cysteamine-induced duodenal ulcers in rats have a very prolonged course of healing. In this study, it was investigated how much the healing of these ulcers is accelerated by some treatments. The treatments included omeprazole, cimetidine, and truncal vagotomy. In addition, the effect of omeprazole and cimetidine on gastric acid secretion was investigated in chronic gastric fistula rats. After 25 days of treatment, significantly more rats in the treated groups had healed ulcers than in the control group. There was little further improvement up to 100 days of treatment, and the difference between treated and untreated groups decreased. The morphology of healing ulcers in treated and untreated rats was also compared. In controls, there was a simultaneous regeneration of mucosa and the submucosal Brunner's glands from the edges of the ulcer, the slow proliferation rate of the latter probably being decisive for the prolonged healing. In the treated rats, the mucosa first regenerated with formation of crypts and low villi and subsequently, the Brunner's glands were formed by proliferation from the bottom of the crypts.     

Correlation between transmucosal potential difference and morphological damage during aspirin injury of gastric mucosa in rats

The potential difference (PD) that is maintained across healthy gastric mucosa is thought to be due to asymmetric ion pumping combined with resistance to back-diffusion of the separated charge. However, the structures that are responsible for this have not been clearly defined. This study examined the temporal changes in PD in rat stomach after injury by a single dose of aspirin. Multiple linear regression was used to compare this with the time course of several parameters of histological damage: (i) the per cent mucosal length showing superficial (confined to surface and gastric pits), deep (involving the isthmus or deeper in oxyntic glands) and total damage; (ii) the number of discrete erosions; and (iii) the total area of erosions per cm sectioned. Mucosal PD fell during the first 30–60 min after aspirin. Superficial damage appeared early and was already recovering by this time. The time course of deep damage more closely matched the alterations in PD and stepwise regression analysis showed that this could be predicted by the amount of deep damage alone (P < 0.001). Changes in transmucosal PD after acute aspirin injury probably reflect damage to structures in the oxyntic glands and not just the breaking of the surface and pit cell ‘barrier’.     

Effects of 24 hours of aspirin, Bufferin, paracetamol and placebo on normal human gastroduodenal mucosa.

Aspirin causes gastroduodenal erosions and/or ulcers in man when taken for prolonged periods. The effects of shorter periods of aspirin, Bufferin, or paracetamol (acetaminophen) intake as used for self-medication are unknown. In a four way, crossover, blinded endoscopic study, we compared the effects of aspirin, Bufferin, paracetamol, and placebo, two tablets four times a day for 24 hours, on the gastroduodenal mucosa of 10 normal volunteers. Both regular aspirin and bufferin produced multiple gastric (p less than 0.005) and duodenal erosions (p less than 0.05, compared with baseline and placebo studies). Paracetamol did not cause significant gastric or duodenal mucosal damage. Two subjects developed duodenal ulcer-like lesions in the course of the study. We conclude that the use of unbuffered aspirin and Bufferin, but not paracetamol, in recommended doses for one day causes significant gastroduodenal mucosal damage.