Interaction of growth hormone-releasing factor and somatostatin on ulcer healing and mucosal growth in rats: role of gastrin and epidermal growth factor

Growth hormone-releasing factor (GRF) was reported to possess the growth-promoting action on the gastroduodenal mucosa that can be augmented by removal of endogenous somatostatin. Since mucosal proliferation was considered to contribute to healing of chronic gastroduodenal ulcerations, we designed the study to determine the interaction of GRF and somatostatin on the healing rate of acetic acid-induced chronic gastric and duodenal ulcers and on the growth of gastroduodenal mucosa in rats. GRF injected subcutaneously twice daily at 100 micrograms/kg/day for 7 days resulted in a significant enhancement of healing rate of both gastric and duodenal ulcerations and this was accompanied by a significant increase in the weight of the mucosa and the contents of RNA and DNA. GRF also significantly increased serum gastrin levels and the tissue contents of epidermal growth factor (EGF) in salivary glands, duodenum and pancreas, suggesting that both gastrin and EGF could contribute to mucosal trophic and ulcer healing effects of GRF. Somatostatin (100 micrograms/kg/day for 7 days) abolished almost completely the ulcer healing and mucosal growth-promoting effects of GRF and this was accompanied by the reduction in serum gastrin level and the tissue contents of EGF suggesting that the suppression of gastrin and EGF release could contribute to the observed effects of somatostatin. We conclude that GRF has both the ulcer healing and the mucosal trophic actions which can be antagonized by somatostatin and that gastrin and EGF may be implicated in these actions.     

Healing of chronic gastroduodenal ulcerations by antacids

Antacids show gastroprotective action against various irritants in experimental animals and enhance the healing of chronic gastroduodenal ulcers in humans but the mechanisms of these effects are unknown. The present study was designed to determine whether prostaglandin (PG) and epidermal growth factor (EGF), which also have protective and antiulcer properties, contribute to the action of antacids on rat's stomach. It was found that Maalox 70 and its active component, Al(OH)₃, enhance significantly the healing of chronic gastric and duodenal ulcers observed during 7 and 14 days after their induction. Pretreatment with indomethacin caused a significant prolongation of ulcer healing, and this was accompanied by a significant reduction in PG and EGF formation, suggesting that both factors may be involved in ulcer healing. Maalox and Al(OH)₃ failed to prevent the suppression of PG by indomethacin but were equally effective in ulcer healing in rats without and with indomethacin administration, suggesting that endogenous PG may not play any important role in the healing process by these drugs. Removal of salivary glands, the major source of EGF, also prolonged ulcer healing but, again, Maalox was as effective in ulcer healing as in rats with intact salivary glands. Our findings that Maalox at pH above 3.0 binds significant amounts of EGF, enhances the binding of EGF to the ulcer area, and stimulates mucosal growth, suggest that EGF may be involved in ulcer healing; however, because antacids are also effective after sialoadenectomy, EGF does not seem to be the major factor in ulcer healing by these drugs.     

Epidermal growth factor (EGF) in the gastroprotective and ulcer healing actions of colloidal bismuth subcitrate (De-Nol) in rats.

Colloidal bismuth subcitrate (CBS; De-Nol) exhibits gastroprotective properties in experimental animals and enhances the healing of chronic gastroduodenal ulcers, but the mechanisms of these actions have not been entirely elucidated. The present study was designed to determine whether epidermal growth factor (EGF), which also has gastroprotective and ulcer healing properties, contributes to the action of De-Nol on the stomach in rats. It was found that De-Nol protects the gastric mucosa against ethanol damage and that this is accompanied by increased mucosal generation of prostaglandins (PG). Removal of the endogenous source of EGF (sialoadenectomy) did not significantly decrease the protective and PG stimulating effects of De-Nol. Pretreatment with exogenous EGF partially protected the stomach against ethanol injury, but did not influence the protective action of De-Nol in sialoadenectomised animals. De-Nol, like EGF given orally, enhanced the healing of chronic gastric and duodenal ulcers induced by serosal acetic acid. De-Nol was found to bind EGF in a pH-dependent manner and to accumulate it in ulcer area. Thus the peptide is available locally in high concentrations to accelerate the re-epithelialisation and tissue repair of the ulcerated mucosa. These ulcer healing effects of De-Nol were reduced by sialoadenectomy and restored in part by oral administration of EGF. We conclude that salivary glands in rats are not essential for the gastroprotection induced by De-Nol, but seem to play an important role in the ulcer healing action of this drug possibly via an EGF mediated mechanism.     

Delayed gastric ulcer healing after extirpation of submandibular glands is sex-dependent

This study examines the effect of excision of the submandibular salivary glands, the main source of epidermal growth factor (EGF), and the role of gender on the healing of acetic acid-induced gastric ulcers in rats. In male rats excision of the submandibular glands delayed ulcer healing. At 15 and 25 days the unhealed ulcer areas were significantly larger in the sialoadenectomy group than in control animals, and fewer completely healed ulcers were seen in this group at 25 days. Ulcer healing in female rats was slower. At day 25 ulcers were healed in 12% of female rats with intact salivary glands, compared with 68% in males. Female rats also showed larger unhealed ulcer areas after sialoadenectomy than controls. We conclude that removal of the main source of EGF in the gastrointestinal tract is associated with a delay in healing of gastric ulcers. The significant difference in healing observed between female and male rats may be influenced by the known androgenic regulation of EGF production in the salivary glands.     

Oral administration of synthetic human urogastrone promotes healing of chronic duodenal ulcers in rats

The effect of oral administration of synthetic human epidermal growth factor/urogastrone (EGF/URO) on healing of chronic duodenal ulcers induced by cysteamine in rats was investigated and compared with that of cimetidine, a H2-receptor antagonist. After 25 and 50 days of treatment, synthetic human EGF/URO significantly increased healing of chronic duodenal ulcers to the same extent as cimetidine. Combined treatment with synthetic human EGF/URO and cimetidine for 25 days was more effective than synthetic human EGF/URO given alone, whereas combined treatment for 50 days was significantly more effective than cimetidine alone. These results show that a combination of an agent inhibiting gastric acid secretion and the cytoprotective and growth-stimulating peptide EGF/URO seems to be more effective with regard to duodenal ulcer healing than individual administration of the two substances. Synthetic human EGF/URO is a potent inhibitor of gastric acid secretion when administered intravenously, but had no effect on acid secretion when given intraduodenally, which suggests that the effect of synthetic human EGF/URO is a direct action on the duodenal mucosa. In conclusion, this study showed that oral synthetic human EGF/URO has a significant effect on healing of duodenal ulcers in rats. The amount of synthetic human EGF/URO administered is comparable to that found in saliva during stimulation of the salivary glands. Our results, therefore, suggest that EGF/URO is one of the endogenous factors participating in healing of duodenal ulcers.     

Effect of sialoadenectomy on gastric mucosal integrity and growth in the rat

The effect of removal of the submandibular-sublingual salivary gland (sialoadenectomy) has been examined in terms of the effects on the susceptibility of the gastric mucosa to the inflammatory and damaging actions of ethanol. In addition, the effects of sialoadenectomy on cell turnover in the gastric mucosa has been examined. Animals were examined at one to five weeks after removal of the submandibular-sublingual salivary gland complex. In response to 100% w/v ethanol, sialoadenectomized rat displayed greater hemorrhagic damage to the gastric mucosa than sham-operated control rats. The difference between sialoadenectomized and sham control rats was significant at two to five weeks after surgery. The rate of [³H]thymidine incorporation into gastric mucosa was significantly reduced in sialoadenectomized rats at one and two weeks. Mucosal DNA concentration was significantly reduced in sialoadenectomized rats at four and five weeks after surgery. Mucosal myeloperoxidase activity was greater in sialoadenectomized rats treated with ethanol compared to control animals, but this difference was only significant at two weeks after surgery. Sialoadenectomy was also associated with a reduction in duodenal and gastric mucosal levels of immunoreactive epidermal growth factor (EGF). Differences between sialoadenectomized and control rats were not significant until three to four weeks after surgery. These data indicate that sialoadenectomy was associated with an increase in the susceptibility of rat gastric mucosa to ethanol-mediated damage. Sialoadenectomy also resulted in a reduction in gastric mucosal growth and gastroduodenal mucosal levels of EGF. However, the influence of sialoadenectomy on the susceptibility of the rat gastric mucosa to ethanol-mediated damage occurred prior to any significant effect on mucosal DNA concentration or EGF levels.This work was supported by a grant from the Medical Research Council of Canada, Grant No. MT6426.     

Role of epidermal growth factor, prostaglandin, and sulfhydryls in stress-induced gastric lesions

Epidermal growth factor promotes the growth of and protects gastric mucosa against various ulcerogens, including stress, but little is known about its role in the pathogenesis of stress ulcerations. In this study, Wistar rats with intact and resected salivary glands were exposed to water-immersion and restraint stress. During 2-14 hours of water-immersion restraint stress, the formation of gastric ulcerations increased progressively and the duration of stress was accompanied by a decrease in DNA synthesis in the gastric mucosa. Following sialoadenectomy, a significant increase in the number of stress ulcerations and further reduction in DNA synthesis were observed. Exogenous epidermal growth factor and dimethyl prostaglandin E2 significantly reduced the ulcerations in the stressed rats with intact salivary glands, but this reduction was significantly less pronounced after sialoadenectomy. Water-immersion restraint stress also resulted in about 50% reduction in mucosal prostaglandin E2 generation, and the pretreatment with indomethacin, which suppressed prostaglandin E2 by about 90%, almost doubled the number of stress ulcerations and abolished the gastro-protective effect of exogenous epidermal growth factor (but not dimethyl prostaglandin E2) against the stress lesions. An inhibition of ornithine decarboxylase activity by difluoromethyl ornithine also augmented stress-induced ulcerogenesis and abolished the protective action of epidermal growth factor while the administration of spermine almost completely prevented stress ulcerations in rats both without and with pretreatment with difluoromethylornithine. Water-immersion restraint stress also significantly reduced mucosal content of glutathione. Cysteamine increased tissue glutathione and reduced stress ulcerations but N-ethylmaleimide, an sulfhydryl blocker, decreased mucosal content of glutathione without affecting the stress ulcerations. This study indicates that the stress ulcers are accompanied by the reduction in mucosal synthesis of DNA, prostaglandin, and glutathione and that the presence of salivary glands attenuates the stress ulcerogenesis probably by releasing epidermal growth factor which acts, in part, by enhancing ornithine decarboxylase activity, mucosal growth, and prostaglandin and glutathione formation.     

Role of submandibular saliva and epidermal growth factor in gastric cytoprotection

The role of submandibular epidermal growth factor in protection of the gastric mucosa was investigated in rats. Removal of the submandibular glands and thereby submandibular epidermal growth factor (EGF) caused rats to develop gastric lesions (ulcerations and ulcers) after administration of the duodenal ulcerogen cysteamine. The median output of EGF in gastric juice was reduced from 45.6 pmol/12 h (total range 17.5-65.0) in unoperated controls to less than 0.06 pmol/12 h (total range less than 0.06-1.82) in rats given cysteamine after extirpation of the submandibular glands. The contents of EGF in the submandibular glands was unchanged during cysteamine treatment. Furthermore, the effects of intragastric instillation of exogenous EGF, infusion of saliva without EGF, and infusion of saliva with a high concentration of EGF on the development of cysteamine-induced gastric lesions were investigated in rats without submandibular glands. Exogenous EGF and saliva with a high but still physiological concentration of EGF significantly reduced the median area in the stomach displaying ulcers and ulcerations, whereas saliva without EGF had no effect. Although EGF is a known inhibitor of gastric acid secretion, the dose used in the present study had no effect on gastric acid secretion in chronic gastric fistula rats; removal of the submandibular glands also did not have any such effect. We conclude that exocrine secretion of submandibular EGF has a cytoprotective function in the stomach, an effect that may be physiological.     

Mucosal expression and luminal release of epidermal and transforming growth factors in patients with duodenal ulcer before and after eradication of Helicobacter pylori.

BACKGROUND: Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF alpha) are potent gastric acid inhibitors and stimuli of mucosal growth and protection but their involvement in Helicobacter pylori associated duodenal ulcer has been little examined. AIM: To assess gastric acid secretion, plasma gastrin concentrations, mucosal content of EGF and TGF alpha, and mucosal expression of these peptides and their receptor (EGFr) as well as salivary and gastric luminal release of EGF under basal conditions and after pentagastrin stimulation in 10 healthy subjects and in 25 H pylori positive patients with duodenal ulcer before and after two weeks of triple anti-H pylori therapy and four weeks after the termination of this therapy. RESULTS: Pentagastrin stimulation caused a significant increase in salivary and gastric release of EGF both in healthy controls and patients with duodenal ulcers but in the patients, the eradication of H pylori resulted in several fold higher gastric luminal (but not salivary) EGF release than before the anti-H pylori therapy. Mucosal contents of immunoreactive EGF and TGF alpha and mucosal expression of EGF, TGF alpha, and EGFr in H pylori positive patients with duodenal ulcer were significantly higher than those in healthy H pylori negative controls and this increase persisted after eradication of H pylori. Basal plasma gastrin was significantly reduced after two weeks of triple therapy and four weeks after the H pylori eradication all ulcers were completely healed. CONCLUSIONS: (1) H pylori infection in patients with duodenal ulcer was accompanied by enhanced plasma gastrin and increased mucosal content and expression of TGF alpha, EGF, and EGFr; (2) H pylori eradication resulted in ulcer healing, reduction in plasma gastrin, and enhancement of gastric (but not salivary) luminal release of EGF, particularly after pentagastrin stimulation; and (3) enhanced mucosal content and expression of TGF alpha, EGF, and EGFr and increased luminal release of EGF may contribute to ulcer healing after eradication of H pylori.     

Gastroprotective and ulcer-healing activities of a new H2-receptor antagonist: ebrotidine.

Ebrotidine is a novel H2-receptor antagonist that exhibits both gastroprotective and ulcer-healing properties. Gastroprotection afforded by ebrotidine against ethanol damage was observed only after intragastric, but not parenteral administration, and it was accompanied by an increase in the mucosal blood flow. Ranitidine given at the same dose (100 mg/kg i.g. or s.c.) did not show any protective activity. When administered twice daily at various doses (1-100 mg/kg) for 10 days, ebrotidine reduced dose dependently the area of chronic gastric ulcers, and it was accompanied by significantly higher contents of epidermal growth factor (EGF) in the ulcer bed than in the intact mucosa. Administration of ranitidine resulted in a similar rate of ulcer healing and in a similar accumulation of EGF in the ulcer area to that observed after ebrotidine, but the increments in plasma gastrin levels in rats treated with ranitidine were observed at lower doses than in tests with ebrotidine. Concurrent administration of indomethacin delayed ulcer healing and reduced the accumulation of EGF in the ulcer area, but did not affect the ulcer healing by ebrotidine or ranitidine. We conclude that ebrotidine but not ranitidine shows gastroprotective activity, but it enhances the healing of chronic ulcerations in a similar manner to ranitidine.     

Effect of oral epidermal growth factor on mucosal healing in rats with duodenal ulcer

AIM: To investigate the effect of epidermal growth factor (EGF) on mucosal healing in rats with duodenal ulcer.METHODS: Male Sprague-Dawley rats were randomly divided into sham operation without EGF, sham operation with EGF, duodenal ulcer without EGF, or duodenal ulcer with EGF groups. Additionally, normal rats without operation served as the control group. Duodenal ulcer was induced in rats by 300 mL/L acetic acid. Rats with EGF were orally administered at a dose of 60 μg/kg/day in drinking water on the next day of operation (day 1). Healing of duodenal ulcer was detected by haematoxylin and eosin staining. Cell growth of damaged mucosa was determined by the contents of nucleic acids and proteins. The level of EGF in duodenal mucosa was measured by ELISA.RESULTS: The pathological results showed that duodenal ulcer rats with EGF improved mucosal healing compared with those without EGF after day 5. Duodenal ulcer rats with EGF significantly increased duodenal DNA content compared with those without EGF on day 15 (6.44±0.54mg/g VS 1.45±0.52 mg/g mucosa, P＜0.05). Duodenal RNA and protein contents did not differ between duodenal ulcer rats with and without EGF during the experimental period.Sham operation and duodenal ulcer rats with EGF significantly increased duodenal mucosal EGF content compared with those without EGF on day 5 (76.0±13.7 ng/g VS 35.7±12.9ng/g mucosa in sham operation rats, and 68.3±10.9 ng/gVS 28.3±9.2 ng/g mucosa in duodenal ulcer rats, P＜0.05).CONCLUSION: Oral EGF can promote mucosal healing of the rats with duodenal ulcer by stimulating mucosal proliferation accompanied by an increase in mucosal EGF content.     

Effect of sialoadenectomy and synthetic human urogastrone on healing of chronic gastric ulcers in rats.

The effect of extirpation of the submandibular glands, an exocrine organ for epidermal growth factor/urogastrone (EGF/URO), and the effect of oral administration of synthetic human (EGF/URO) on healing of chronic gastric ulcers in rats has been investigated. Removal of the submandibular glands delayed healing of chronic gastric ulcers when examined after 50, 100, and 200 days. Oral administration of synthetic human EGF/URO stimulated gastric ulcer healing when examined after 25 and 50 days of treatment. The effect of synthetic human EGF/URO was comparable with that of cimetidine. The combined administration of synthetic human EGF/URO and cimetidine further increased healing of gastric ulcers compared with administration of each substance. Neither synthetic human EGF/URO, nor removal of the submandibular glands had any influence on gastric acid secretion. This study showed that the submandibular glands influence healing of chronic gastric ulcers and suggest that EGF/URO participate in healing of chronic gastric ulcers in rats.     

Epidermal Growth Factor in Gastric Ulcer Healing by Nocloprost,a Stable Prostaglandin E2 Derivative

Background: The gastroprotective and ulcer-healing properties of prostaglandins, especially in gastric ulcers induced by non-steroidal anti-inflammatory drugs, are well established. Ulcer healing is an active process of filling the mucosal defect with migrating and proliferating epithelial cells combined with angiogenesis in granulation tissue at the ulcer bed. Growth factors, especially epidermal growth factor (EGF) and transforming growth factor alpha (TGFa) are crucial in the regulation of the reconstruction of damaged mucosal structures. Methods: In this double-blind, randomized, prospective study 40 patients with gastric ulcer were treated with nocloprost, a stable prostaglandin E₂ derivative, or with ranitidine. All subjects underwent endoscopy before and after 4 and 8 weeks of anti-ulcer therapy. During endoscopy mucosal biopsies were performed for determination of EGF content in gastric mucosa at the ulcer margin and in the intact mucosa. Additionally, EGF output in saliva and its plasma concentrations were determined in all subjects before and during the treatment. Results: The gastric ulcer healing rate after 4 weeks was significantly higher in patients treated with nocloprost than in those treated with ranitidine (63% versus 39%, respectively). At initial examination the EGF content in the gastric mucosa obtained from the ulcer edge was significantly higher than that in the intact mucosa. There was a significant increase in the EGF content in both the ulcer margin and the intact mucosa in subjects treated with nocloprost but not in patients under treatment with ranitidine. Similarly, patients treated with nocloprost had significantly higher EGF output in saliva and higher EGF concentration in plasma throughout the anti-ulcer therapy. Conclusion: Nocloprost is superior to ranitidine in the treatment of chronic gastric ulcers, and these effects could be due, at least in part, to higher expression and mucosal content of EGF in the ulcer area.     

Effect of cell proliferation on healing of gastric and duodenal ulcers in rats

The healing of acetic acid-induced gastric and duodenal ulcers was examined together with the biochemical indices of growth in gastric and duodenal mucosa in the following three groups of rats: (a) chow-fed, (b) fed an isocaloric liquid diet, (c) fed the liquid diet plus pentagastrin injections (250 micrograms/kg, 3 times/day). Animals received the diet regimen for 10 days from 1 day after induction of ulcer (day 0). Following the feeding regimens, serum gastrin levels, oxyntic gland mucosal DNA synthesis, and gastric secretory function were significantly lowered in the rats fed liquid diets. DNA synthesis in the duodenal mucosa was not different from the pre-ulcer levels. Pentagastrin significantly restored the DNA synthetic and gastric secretory activity of the liquid diet-fed rats toward the levels in the chow-fed group. In the latter group, a significant increase in DNA synthesis and levels of serum gastrin was found at day 6 (after 5 days feeding), which corresponded with a rapid, spontaneous healing of ulcers. Feeding rats liquid diet significantly delayed the healing of gastric, but not duodenal ulcers. Repeated administration of pentagastrin accelerated gastric ulcer healing in the liquid diet group toward the rate observed in the chow-fed group, but had no effect on the healing of duodenal ulcers. These results indicate that cell proliferation is an important factor in the healing of gastric ulcers.     

Effect of sialoadenectomy on adaptive cytoprotection in the rat

In the present study we have investigated the effect of sialoadenectomy in the rat on adaptive cytoprotection induced by intragastric instillation of an irritant concentration of ethanol (10% wt/vol). Gastric mucosae were examined 1 h after oral administration of 100% ethanol. In animals with intact salivary glands, pretreatment with saline was followed 15 min later by 100% ethanol. This treatment was associated with a significant degree of mucosal damage. However, prior administration of 10% ethanol in place of saline reduced the area of ulceration. In sialoadenectomized rats, the irritant concentration of ethanol did not protect the gastric mucosa from the damaging actions of absolute ethanol. The effect was partially restored if sialoadenectomized rats were treated for 3 days with an aqueous extract of rat salivary gland tissue. Histologic examination revealed no differences in the extent of epithelial damage or adherent mucus between rats with intact salivary glands and sialoadenectomized rats following pretreatment with either saline or 10% ethanol. Although adaptive cytoprotection in animals with intact salivary glands was not associated with increases in mucosal capacities for prostaglandin E2 or 6-keto prostaglandin F1 alpha biosynthesis, sialoadenectomy resulted in a reduction in the mucosal biosynthetic capacities for both prostanoids. Salivary gland extract administration to sialoadenectomized rats did not significantly alter mucosal prostaglandin biosynthesis levels. These data suggest that salivary gland factors affected adaptive cytoprotection induced by an irritant dose of ethanol. Although endogenous prostaglandin biosynthesis capabilities do not appear to be altered in adaptive cytoprotection, salivary factors appear to influence mucosal generation of prostaglandins.     

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.     

Impairment of Gastric Ulcer Healing by Alendronate,a Nitrogen-Containing Bisphosphonate,in Rats

Bisphosphonates such as alendronate have been developed as antiresorptive agents capable of treating diseases related to bone remodeling. In the present study, we examined the effect of alendronate on the healing of acetic acid-induced gastric ulcers in rats and investigated the mechanism involved in this action both in vivo and in vitro using the rat gastric epithelial cell line (RGM1). Acetic acid-induced gastric ulcers healed spontaneously, with up-regulation of COX-2/prostaglandin E₂ production as well as expression of vascular endothelium-derived growth factor (VEGF) and basic fibroblast growth factor (bFGF) in ulcerated mucosa. The healing of ulcers was impaired by indomethacin (2 mg/kg, s.c.) or alendronate (60 mg/kg, p.o.) given once daily for 7 days, starting 3 days after acid application. Indomethacin, but not alendronate, inhibited mucosal prostaglandin E₂ production. Alendronate as well as indomethacin decreased the protein expression of both VEGF and bFGF in ulcerated mucosa, resulting in a reduction of angiogenesis in the ulcer base. Supplementation of recombinant bFGF significantly reverted the delay in ulcer healing caused by alendronate. On the other hand, the size of cell-free areas in RGM1 cells in vitro decreased with time after wound induction, and this process was promoted by epidermal growth factor (EGF; 10 ng/ml). Co-incubation with alendronate (1 mM) did not affect the spontaneous healing but significantly suppressed the accelerated wound healing caused by EGF. These results suggest that alendronate impairs the healing of gastric ulcers in rats, and this effect may be related to down-regulation of VEGF and bFGF, the important growth factors for vascularization/granulation, as well as suppression of the stimulatory action of EGF on epithelial proliferation/migration.     

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.     

Metabolism of oral trefoil factor 2 (TFF2) and the effect of oral and parenteral TFF2 on gastric and duodenal ulcer healing in the rat

BACKGROUND: Trefoil factors (TFFs) are peptides produced by mucus-secreting cells in the gastrointestinal tract. A functional association between these peptides and mucus, leading to stabilisation of the viscoelastic gel overlying the epithelia, has been suggested. Both oral and parenteral administration of the peptides increase the resistance of the gastric mucosa. AIM: To study the effect in rats of oral and parenteral porcine trefoil factor 2 (pTFF2) on the healing of gastric and duodenal ulcerations and to clarify the distribution and metabolism of orally administered pTFF2 in the gastrointestinal tract. METHODS: Gastric ulcers were induced in female Sprague-Dawley rats by indomethacin and duodenal ulcers by mercaptamine. The rats were treated for up to seven days with oral or subcutaneous pTFF2. Ulcer size after treatment was assessed by stereomicroscopy after whole mount staining with periodic acid-Schiff stain. (125)I-labelled pTFF2 was given orally to rats, and tissues were investigated by gamma counting of samples and by autoradiography of paraffin embedded sections. RESULTS: pTFF2 accelerated gastric ulcer healing after both oral and subcutaneous administration. Duodenal ulcers were aggravated by both treatments. After oral administration of (125)I-pTFF2, intact peptide was recovered from the superficial part of the mucus layer in the stomach; it passed through the small intestine but was degraded in the caecum. Only a minor part of the labelled pTFF2 entered the colon and was excreted in the faeces. Most of the label was excreted in the urine. CONCLUSIONS: Oral as well as parenteral pTFF2 accelerates the healing of gastric ulceration and aggravates duodenal ulcers. Oral pTFF2 binds to the mucus layer of the stomach and the small intestine but does not reach the colonic mucosa.     

Influence of gastric colonization with Candida albicans on ulcer healing in rats: effect of ranitidine, aspirin and probiotic therapy

OBJECTIVE: Candida albicans frequently inhabits the gastrointestinal tract of humans leading to gastrointestinal candidiasis, especially following suppression of gastric acidity, but studies on the relation between this fungal infection and gastric pathology are limited due to lack of convenient animal models resembling Candida infection in humans. MATERIAL AND METHODS. We compared the effects of C. albicans and vehicle inoculation on gastric secretion and healing of gastric ulcers induced by acetic acid in rats treated with 1) ranitidine (30 mg kg(-1) day(-1) s.c.) and 2) aspirin (ASA) (60 mg kg(-1) day(-1) i.g.) with or without probiotic bacteria Lactobacillus acidophillus. At day 0 and at 4, 15 and 25 days after ulcer induction, the ulcer area, the gastric blood flow (GBF), the quantitative gastric cultures of Candida and the expression of mRNAs for pro-inflammatory cytokines IL-1beta and TNF-alpha and growth factors EGF and TGFalpha were assessed in the gastric mucosa. RESULTS: Gastric acid output was reduced by over 40% soon after Candida inoculation and this effect persisted during all time intervals tested. The area of ulcers in control rats significantly decreased at day 15 and the ulcers disappeared almost completely after 25 days of their induction. In contrast, the ulcers were present until day 25 in Candida-inoculated rats followed by a fall in GBF and a rise in plasma gastrin levels, these effects being significantly attenuated by the co-treatment with Lactobacillus. Candidiasis was accompanied by up-regulation of mRNA for IL-1beta, TNF-alpha, EGF and TGFalpha and a significant increment in plasma IL-1beta and TNF-alpha levels. CONCLUSIONS: 1) Persistent colonization with Candida could be achieved in rats treated with antisecretory agents or non-steroidal anti-inflammatory drugs (NSAIDs) such as ASA; 2) candidiasis reduces gastric acid secretion, while delaying ulcer healing possibly due to the impairment in GBF in the ulcer area and enhanced expression and release of IL-1beta and TNFalpha and 3) probiotic therapy could be useful in the treatment against the deleterious action of fungal infection on the healing of pre-existing gastric ulcers.