Healing Of Gastric Ulcers In Rats Research Articles

Effect of H. pylori status on gastric ulcer healing in patients continuing nonsteroidal anti-inflammatory therapy and receiving treatment with lansoprazole or ranitidine

OBJECTIVES: The purpose of this research was to determine the impact of pretreatment Helicobacter pylori infection on gastric ulcer healing rates in patients receiving nonsteroidal anti-inflammatory drugs (NSAIDs) and antisecretory medications. METHODS: This was a pooled, prospective analysis of two identical double blind, multicenter, parallel group studies. Six hundred ninety-two patients receiving NSAIDs and with endoscopy-documented gastric ulcers were enrolled from 90 North American sites in primary care and referral centers. Patients were randomized to receive ranitidine (150 mg b.i.d.) or lansoprazole (15 mg or 30 mg once daily) for 8 wk. Ulcer healing was assessed by endoscopy at 4 and 8 wk in an intent-to-treat population. H. pylori status was determined at baseline by histology. RESULTS: Across all three treatment groups, gastric ulcers were more likely to heal and heal faster if the individual was infected with H. pylori. Healing rates at 8 wk were statistically significantly greater among H. pylori positive patients (n = 181) than among negative patients (n = 497) (70% vs 61%, respectively; p < 0.05), especially among those with large ulcers (>10 mm) and in younger patients (<60 yr old). Simple healing rates (regardless of H. pylori status) were significantly better in the 15- and 30-mg lansoprazole groups than in the ranitidine group after 4 wk (46%, 54%, and 32%, respectively; p ≤ 0.01) and 8 wk (66%, 74%, and 50%, respectively; p < 0.001). CONCLUSIONS: In patients receiving NSAIDs, gastric ulcer healing with an antisecretory agent is significantly enhanced in the presence of H. pylori infection.

Antiangiogenic Effect of a Highly Selective Cyclooxygenase-2 Inhibitor on Gastric Ulcer Healing in Rats

Selective cyclooxygenase-2 (COX-2) inhibitors have been shown to produce fewer gastrointestinal adverse reactions when compared with conventional nonselective nonsteroidal anti-inflammatory drugs and they suppress angiogenesis in tumors. The purpose of the present study was to investigate the effects of highly selective COX-2 inhibitor on angiogenesis and protein expression of angiogenic factor during gastric ulcer healing. Gastric ulcers were induced in male Sprague–Dawley rats by a luminal application of acetic acid solution. Rofecoxib, a selective COX-2 inhibitor, was administered at a dose of 10 mg/kg/day by gastric intubation for 14 successive days. The ulcer size was measured at different time intervals after ulcer induction. The microvessels that were immunohistologically positive for von Willebrand factor within the ulcer bed were counted. The protein levels of basic fibroblast growth factor (bFGF) and concentration of prostaglandin E 2 (PGE 2) in the ulcer tissues were analyzed with Western blotting and immunoassay methods, respectively. The results demonstrated that rofecoxib treatment significantly increased the ulcer size at days 6, 10, and 15. It decreased the number of microvessels, bFGF protein expression, and PGE 2 level in the ulcer base at day 6. The findings that highly selective COX-2 inhibitor delayed ulcer healing in rats and impaired angiogenesis in the ulcer base raise cautions regarding the use of COX-2 inhibitors in patients with gastric ulcers.

Are proton pump inhibitors the first choice for acute treatment of gastric ulcers? A meta analysis of randomized clinical trials

BackgroundGastric ulcers are a frequent problem in the United States. Proton pump inhibitors have been shown to increase healing rates and improve clinical symptoms. The objective of this study is to compare gastric ulcer healing rates for patients treated with a proton pump inhibitor (PPI) (omeprazole, rabeprazole, pantoprazole, or lansoprazole), an histamine 2- receptor antagonist (ranitidine) or placebo.MethodsA literature search was conducted to identify randomized, controlled clinical trials that included a PPI in at least one treatment arm and assessed the gastric ulcer healing rates endoscopically. The healing rates were estimated for each treatment at specific time points, and Rate Ratios (RR) and 95% confidence intervals (CI) were estimated for each trial.ResultsSixteen trials met the inclusion criteria: four compared a PPI versus placebo, nine compared a PPI versus ranitidine (no trials of rabeprazole versus ranitidine met the inclusion criteria), and three compared a newer PPI (lansoprazole, pantoprazole or rabeprazole) versus omeprazole. In relation to ranitidine, the pooled RR of PPIs (lansoprazole, omeprazole and pantoprazole) was 1.33 (95% CI 1.24 to 1.42) at four weeks. In each trial, greater improvement in the studied clinical symptoms was found with the newer PPIs (rabeprazole, pantoprazole and lansoprazole) when compared to omeprazole.ConclusionIn this study treatment with PPIs resulted in higher healing rates than ranitidine or placebo. This evidence suggests that the first choice for gastric ulcer treatment for the greater relief of symptoms is one of the newer PPIs.

Chronic gastric ulcer healing in rats subjected to selective and non-selective cyclooxygenase-2 inhibitors

The influence of different nonsteroidal anti-inflammatory drugs (NSAIDs) and of a proton pump inhibitor on the healing parameters of a chronic gastric ulcer was evaluated. Wistar rats were used after the induction of a chronic acetic acid ulcer. The animals were treated orally for 8 and 15 days, twice daily, with the conventional NSAID, piroxicam (0.35 mg/kg), the non-narcotic analgesic, metamizol (33 mg/kg), the selective cyclooxygenase-2 inhibitor, celecoxib (1.8 mg/kg) and the proton pump inhibitor, omeprazole (0.35 mg/kg). Macroscopic ulcer index, myeloperoxidase activity and prostaglandin E 2 content (both biochemical parameters were evaluated in ulcerated and in intact tissue) as well as histological and immunohistochemical evaluations were carried out at 8 and 15 days. Omeprazole accelerated ulcer healing at 8 and 15 days ( P<0.05), while celecoxib delayed healing significantly at 15 days ( P<0.01). At 8 days, the prostaglandin E 2 content decreased with all NSAIDs at the ulcer site as well as in intact tissue. The same happened at 15 days except for celecoxib, which only diminished prostaglandins in intact mucosa. Immunohistochemistry showed differences in the location of cyclooxygenase-2 and -1. The highest cyclooxygenase-2 expression was found with piroxicam and the lowest expression was with celecoxib. Conclusions: Down-regulation of cyclooxygenase-2 expression as well as a possible involvement of the chemical structure of celecoxib, a 1,5-dirarylpirazole with a sulphonamide moiety, may account for the delay in ulcer healing.

Effects of NSAIDs on cryoprobe-induced gastric ulcer healing in rats.

Failure of ulcer healing may be critically important to the development of serious gastrointestinal complications in patients on long-term NSAIDs. To determine the effect of indometacin, celecoxib, a cyclooxygenase-2-specific inhibitor, and nabumetone, a pro-drug, on ulcer healing rates in the rat. Gastric ulcers were induced using a cryoprobe. An NSAID or a vehicle control was administered to groups of eight rats for 3 or 6 days (2 mg/kg indometacin, 9 mg/kg celecoxib or 40 mg/kg nabumetone). The ulcer area was measured and epithelial proliferation at the ulcer margins was measured histochemically. The effect of the drugs on intestinal prostaglandin levels was also assessed. The mean ulcer sizes in the four groups on day 3 were comparable. On day 6, control animals and those receiving nabumetone showed significant ulcer healing (P < 0.02), while the mean ulcer sizes in the indometacin (P < 0.01) and celecoxib (P < 0.02) groups were significantly larger than those in the control group. Higher doses of nabumetone (160 mg/kg), however, impaired healing. Intestinal prostaglandins were reduced (P < 0.01) only in indometacin-treated animals. The epithelial proliferation index was significantly lower among indometacin- (P=0.02) and celecoxib-treated (P=0.03) animals compared to controls at day 3. Celecoxib and indometacin both decreased the epithelial proliferative response and delayed healing of cryoprobe-induced gastric ulcers. In contrast, nabumetone impaired ulcer healing only at very high doses.

A 3.0-kDa low molecular weight heparin promotes gastric ulcer healing in rats.

Previous studies have shown that intragastric administration of unfractionated heparin enhances gastric ulcer healing in rats. As the large molecule of heparin may be partially degraded in the upper gastrointestinal tract, it is likely that fragments of heparin, derived from the unfractionated parent compound, are involved in the anti-ulcer action in the stomach. Therefore, it is possible that low molecular weight heparin may have a similar ulcer healing effect. Male Sprague-Dawley rats with acetic acid-induced gastric ulcers were given a 3.0-kDa low molecular weight heparin (0.6-6.0 mg/kg) intravenously or intragastrically once daily for 4 days. Ulcer healing, mucosal histological changes, angiogenesis and gastric mucus production both in vivo and in vitro were determined. The bleeding time was measured to indicate the anticoagulation activity. Both intravenous and intragastric low molecular weight heparin dose dependently accelerated gastric ulcer healing, which was accompanied by a significant increase in mucosal regeneration and proliferation, angiogenesis and mucus content in the stomach. The drug also stimulated the mucus production in MKN-28 cells. Drug administration by either route did not alter the bleeding time in rats. A 3.0-kDa low molecular weight heparin possesses an ulcer healing effect similar to that of unfractionated heparin in the stomach of the rat. This smaller molecular drug is superior to the unfractionated form, does not affect the coagulation activity and may show better absorption in the gastrointestinal tract.

Management of gastroduodenal ulcers and gastrointestinal symptoms associated with nonsteroidal anti-inflammatory drug therapy: A summary of four comparative trials with omeprazole, ranitidine, misoprostol, and placebo

Background: Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective in the treatment of systemic diseases such as rheumatoid arthritis but are associated with a range of adverse gastrointestinal (GI) side effects, including dyspepsia, peptic ulcer, and ulcer complications. Several studies have compared the relative efficacy and tolerability of omeprazole, ranitidine, and misoprostol in the management of NSAID-associated GI adverse events. Objective: The purpose of this paper is to summarize and evaluate the results of 4 clinical studies that compared the efficacy and tolerability of omeprazole, misoprostol, and ranitidine in the acute and maintenance treatment of NSAID-associated gastroduodenal ulcers and GI symptoms. Methods: The 4 trials, which included 1822 patients being treated continuously with NSAIDs, studied omeprazole (20 and 40 mg once daily) as acute treatment for healing gastroduodenal ulcers and erosions and as prophylaxis (20 mg once daily) over 3 to 6 months. Comparators were misoprostol 200 μg 4 times daily or ranitidine 150 mg twice daily in the acute phases and misoprostol 200 μg twice daily, ranitidine 150 mg twice daily, or placebo in the prophylactic phases. Results: Gastric and duodenal ulcer healing rates were higher with omeprazole than with either misoprostol ( P = 0.004 for gastric ulcers; P < 0.001 for duodenal ulcers) or ranitidine ( P < 0.001 for gastric ulcers; P = 0.032 for duodenal ulcers). A significantly larger percentage of patients taking misoprostol had the number of gastric or duodenal erosions reduced from >10 to <5 compared with patients taking omeprazole ( P < 0.001), whereas a significantly larger percentage of patients taking omeprazole achieved the same reduction in number of erosions compared with patients taking ranitidine ( P = 0.008). More patients taking omeprazole remained in remission than patients taking misprostol ( P = 0.001), ranitidine ( P = 0.004), or placebo ( P < 0.001). More patients taking misoprostol (16.9%) or ranitidine (14.1%) discontinued treatment because of adverse events, lack of efficacy, or other reasons compared with patients taking omeprazole (9.9% and 10.2% in 2 studies). Conclusions: Omeprazole was more effective in healing and prophylaxis of NSAID-associated gastroduodenal ulceration and symptoms than misoprostol and ranitidine in chronic NSAID users, and was better tolerated than misoprostol.

Role of nuclear factor-kappaB in gastric ulcer healing in rats.

We investigated the role of nuclear factor-kappaB (NF-kappaB) in gastric ulcer healing in rats. NF-kappaB was activated in ulcerated tissue but not in normal mucosa, and the level of the activation was decreased with ulcer healing. NF-kappaB activation was observed in fibroblasts, monocytes/macrophages, and neutrophils. Treatment of gastric fibroblasts, isolated from the ulcer base, with interleukin-1beta activated NF-kappaB and the subsequently induced cyclooxygenase-2 and cytokine-induced neutrophil chemoattractant-1 (CINC-1) mRNA expression. Inhibition of activated NF-kappaB action resulted in suppression of both their mRNA expression and increases in PGE(2) and CINC-1 levels induced by interleukin-1beta. Persistent prevention of NF-kappaB activation caused an impairment of ulcer healing in rats. Gene expression of interleukin-1beta, CINC-1, cyclooxygenase-2, and inducible nitric oxide synthase in ulcerated tissue had been inhibited before the delay in ulcer healing became manifest. The increased levels of cyclooxygenase-2 protein and PGE(2) production were also reduced. These results demonstrate that NF-kappaB, activated in ulcerated tissue, might upregulate the expression of healing-promoting factors responsible for gastric ulcer healing in rats.

A mechanistic study of proliferation induced by Angelica sinensis in a normal gastric epithelial cell line

It has been reported that an extract from Angelica sinensis mainly consisting of polysaccharides (95%) prevented ethanol- or indomethacin-induced gastric mucosal damage (Cho CH et al. Planta Med 2000;66:348–51). However, it is not known whether Angelica sinensis has a direct stimulatory effect on the healing of gastric mucosal lesions. To study the hypothesis that Angelica sinensis has a direct mucosal healing effect in rats and in isolated gastric epithelial cells, we assessed the wound repair in both animals and normal cell culture (RGM-1), as well as [ 3H]thymidine incorporation, ornithine decarboxylase (ODC) activity, and ODC protein and c-Myc protein expression after different treatments in RGM-1 cells. We found that Angelica sinensis crude extract (ASCE) dose-dependently enhanced gastric ulcer healing in rats and promoted wound repair in RGM-1 cells. It also significantly stimulated [ 3H]thymidine incorporation and ODC activity in RGM-1 cells in a concentration-dependent manner. ODC and c-Myc protein expression was also increased as a result of this process. dl-α-difluoromethyl-ornithine repressed the [ 3H]thymidine incorporation and ODC activity induced by ASCE. Pretreatment with c-Myc antisense oligodeoxynucleotides blocked the stimulatory action of ASCE on [ 3H]thymidine incorporation and ODC protein expression. These data suggest that ASCE has a direct mucosal healing effect on gastric epithelial cells, while ODC and c-Myc are closely associated with this effect.

Expression of gene for EIIIA- and EIIIB- fibronectin, fetal types of fibronectin, during gastric ulcer healing in rats.

Fibronectin (FN) is important for wound healing via cell proliferation, adhesion, differentiation, and matrix formation. Fetal types of FN mRNA, which include the region of EIIIA or EIIIB, are well expressed during embryonic development and wound healing. This study was done to investigate the mRNA expression of full-length FN, EIIIA- and EIIIB-FN, and the localization of FN in the gastric tissues during ulcer healing with northern blot analysis and immunohistochemical technique. Gastric ulcers in rats were produced by acetic acid. EIIIA- and EIIIB-FN mRNA were not detected in normal gastric tissues, but were expressed in the ulcerated tissues throughout the healing phase. However, on day 60 (in the scarred phase), the EIIIA- and EIIIB-FN mRNA had disappeared. The levels of full-length FN mRNA were increased from day 3 to 32 compared with the control levels, and decreased to the control levels on day 60. Full-length FN was predominantly localized at the mesenchyme around the infiltrating inflammatory cells in the granulation tissues and the basement membranes of the nonproliferating epithelial cells, which were regenerated at the ulcer margin. Thus, fetal gene transcripts of FN suggest the important role of fetal FN in gastric ulcer healing, mainly via the migration of mesenchymal and epithelial cells.

Endothelial nitric oxide synthase modulates gastric ulcer healing in rats.

Nitric oxide has been shown to be beneficial for gastric ulcer healing. We determined the relative effects of endothelial and inducible nitric oxide synthases on gastric ulcer healing in rats. Ulcers were induced by serosal application of acetic acid. Ulcer severity, angiogenesis, and nitric oxide synthase expression were assessed 3-10 days later. The effects of inhibitors of nitric oxide synthase were also examined. Inducible nitric oxide synthase mRNA was only detected in ulcerated tissue (maximal at day 3), whereas the endothelial isoform mRNA was detected in normal tissue and increased during ulcer healing. Inducible nitric oxide synthase was expressed in inflammatory cells in the ulcer bed, whereas endothelial nitric oxide synthase was found in the vascular endothelium and in some mucosal cells in both normal and ulcerated tissues. Angiogenesis changed in parallel with endothelial nitric oxide synthase expression. N(6)-(iminoethyl)-L-lysine did not affect angiogenesis or ulcer healing, while N(G)-nitro-L-arginine methyl ester significantly reduced both. In conclusion, endothelial nitric oxide synthase, but not the inducible isoform, plays a significant role in gastric ulcer healing.

Intragastric administration of heparin enhances gastric ulcer healing through a nitric oxide-dependent mechanism in rats

Our preliminary finding indicated that intravenous (i.v.) injection of heparin increased gastric ulcer healing in rats. However, the anticoagulant action of i.v. heparin could produce complications in ulcer patients if the drug was used as an anti-ulcer agent. The present study aimed to investigate whether intragastric (i.g.) administration of heparin, known to have no anticoagulant activity, would have the similar ulcer healing effect and the relationship of this effect, if any, with nitric oxide (NO), a substance suggested to be important for ulcer healing. Heparin (100, 500, 1000 U/kg, i.g.) administered once daily for 4 days accelerated the healing of gastric ulcer induced by acetic acid in Sprague–Dawley rats, which was accompanied by an increase in mucosal proliferation and regeneration at the ulcer margin, microvessel number both at the ulcer margin and base, and the thickness of mucus layer. Both activity and content, but not the mRNA of constitutive nitric oxide synthase (cNOS) in the gastric mucosa were enhanced. l-N G-nitroarginine methyl ester ( l-NAME), an inhibitor of NOS activity blocked the cNOS activity activated by heparin and reversed the beneficial effects of heparin on ulcer healing. The bleeding time was not altered by i.g. heparin. These findings demonstrate that i.g. heparin promotes the healing processes of gastric ulcer. Such effect is suggested to act through the stimulation of mucosal cNOS activity. In addition, i.g. heparin is better than i.v. heparin without the potential anticoagulation effect.

Inhibitory effects of the angiogenesis inhibitor TNP-470 on gastric ulcer healing in rats

Inhibitory effects of the angiogenesis inhibitor TNP-470 on gastric ulcer healing in rats

Pentoxifylline Accelerates Gastric Ulcer Healing in Rats: Roles of Tumor Necrosis Factor Alpha and Neutrophils during the Early Phase of Ulcer Healing

Background/Aims: Pentoxifylline has many anti-inflammatory properties including inhibition of production of tumor necrosis factor alpha (TNF-α). Although pentoxifylline prevents several types of gastric mucosal injury, the effect of this drug on ulcer healing is unknown. In this study, we examined the effect of pentoxifylline on healing of acetic acid induced gastric ulcers in rats. Methods: Rats with gastric ulcer received an intraperitoneal injection of 10 mg/kg pentoxifylline once daily for 14 days or for only the first 7 days or the last 7 days of the 14-day treatment period. Some rats were given antirat neutrophil antiserum intraperitoneally every other day. Ulcer size, myeloperoxidase activity, and concentration and location of TNF-α in ulcer tissue were assessed. Results: Administration of pentoxifylline for 14 days or for the first 7 days, but not for the last 7 days, of the 14-day treatment period accelerated ulcer healing. TNF-α was detected mainly in monocytes/macrophages and in some neutrophils at ulcer bases and margins. Pentoxifylline markedly decreased the concentration of TNF-α as well as the myeloperoxidase activity in ulcer tissue on days 2 and 4. Antirat neutrophil antiserum inhibited neutrophil infiltration into ulcer tissue and accelerated ulcer healing. Conclusion: Pentoxifylline accelerates healing of acetic acid induced gastric ulcer in rats. This effect may be due in part to reduction of neutrophil infiltration and inhibition of production of TNF-α by inflammatory cells. Early-phase inhibition of inflammatory response may accelerate ulcer healing.

Sequential expression of adrenomedullin and its receptor during gastric ulcer healing in rats.

Adrenomedullin (AM) is a potent vasodilatory peptide. While its growth-regulating action in some cultured cells has been recognized, expression of AM and its receptor during gastric ulcer healing has not been explored. Specimens of gastric walls from control rats or gastric ulcers were obtained at 1, 3, 7, and 14 days after gastric ulcer induction. AM and its receptor mRNAs expression were determined by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. By RT-PCR, AM mRNA was increased by 167% at three days, while AM receptor mRNA was increased by 234% at seven days (both P < 0.05). By in situ hybridization, AM and AM receptor mRNAs were increased at ulcer margin from three days after ulcer induction. By immunohistochemistry, AM was increased in the ulcer margin at three and seven days. In separate in vitro studies using a rat gastric epithelial (RGM1) cell line, AM treatment significantly increased transforming growth factor-alpha mRNA expression and cell proliferation.

O-107 - Role of p38 in gastric ulcer healing in rats

O-107 - Role of p38 in gastric ulcer healing in rats

Antiulcerogenic mechanisms of dehydrocrotonin, a diterpene lactone obtained from Croton cajucara.

The bark of Croton cajucara Benth, is used in Brazilian folk medicine as an infusion to treat gastrointestinal disorders. The aim of the present study was to assess the mechanisms involved in the antiulcerogenic activity of dehydrocrotonin (DHC), a diterpene isolated from C. cajucara bark. We studied the effects of DHC on pylorus ligature (Shay) in mice treated with the drug (100 mg/kg) by the intraduodenal route. DHC did not induce any alteration in gastric volume in Shay mice but modified the pH and total acid concentration of gastric juice. Incubation of gastric juice with DHC did not reduce gastric acidity compared to control. We also investigated the effects of DHC on the response to histamine of right atria isolated from guinea pigs and on the response to carbachol of stomach fundus strips from rats. The concentration-response curves for the chronotropic effect of histamine in guinea pig right atria were shifted to the right, with a significant decrease in the maximum response, in the presence of DHC. Similar results were obtained with DHC (30 microM) for the concentration-response curves to carbachol in the isolated rat stomach. The ability of DHC to increase PGE2 release from rat stomach mucous cells was also studied. We observed that DHC induced a significant increase in PGE2 production (60% compared to control). In addition, the effects of DHC on the healing of acetic acid-induced gastric ulcer in rats were evaluated 14 days after acid injection. Oral administration of DHC (100 mg/kg per day) for 14 consecutive days had no effect on gastric ulcer healing in rats. Thus, the protective effect of DHC on induced gastric lesions could be due to synergistic effects, e.g., an increase in PGE2 release and non-competitive antagonism of H2-receptors and of muscarinic receptors. Whereas the former result represents an increase in the protective factors, the latter one shows a decrease in the aggressive factors against the gastric mucosa.

Roles of IL-1β and TNF-α in gastric ulcer healing in rats

Roles of IL-1β and TNF-α in gastric ulcer healing in rats

Relationship between vascular endothelial growth factor and angiogenesis in gastric ulcer healing in rats

Relationship between vascular endothelial growth factor and angiogenesis in gastric ulcer healing in rats

Role of Thromboxane A2 in Healing of Gastric Ulcers in Rats

We investigated the role of thromboxane (TX) A2 in gastric ulcer healing in rats. Acetic acid ulcers were produced in male Donryu rats. TXA2 synthesis in the stomachs with ulcers was significantly elevated in ulcerated tissue, but not in intact tissue, compared with that in the gastric mucosa of normal rats. Indomethacin inhibited both TXA2 and prostaglandin E2 (PGE2) synthesis in ulcerated tissue, while NS-398 (selective cyclooxygenase-2 inhibitor) reduced only PGE2 synthesis. OKY-046 (TXA2 synthase inhibitor) dose-relatedly inhibited only TXA2 synthesis. The maximal effect of OKY-046 (80% inhibition) was found at more than 30 mg/kg. When OKY-046 was administered for 14 days, the drug at more than 30 mg/kg significantly accelerated ulcer healing without affecting acid secretion. The maximal reduction of ulcerated area by OKY-046 was about 30%, compared with the area in the control. Histological studies revealed that regeneration of the mucosa was significantly promoted by OKY-046, but neither maturation of the ulcer base nor angiogenesis in the base were affected. OKY-046 and TXB2 had no effect on proliferation of cultured rat gastric epithelial cells, but U-46619 (TXA2 mimetic) dose-relatedly prevented the proliferation without reducing cell viability. These results indicate that the increased TXA2, probably derived from cyclooxygenase-1 in ulcerated tissue, exerts a weak inhibitory effect on ulcer healing in rats. The effect of TXA2 might be due partly to prevention of gastric epithelial cell proliferation at the ulcer margin.