Pathogenesis of gastric lesions induced by aspirin in the pylorus-ligated rat

Nitric oxide, afferent sensory nerves, and antioxidative enzymes in the mechanism of protection mediated by tricarbonyldichlororuthenium(II) dimer and sodium hydrosulfide against aspirin-induced gastric damage

BACKGROUND

Aspirin exerts side effects within the gastrointestinal tract. Hydrogen sulfide (H₂S) and carbon monoxide (CO) have been implicated in gastroprotection but the mechanism of beneficial action of these gaseous mediators against aspirin-induced damage has not been fully studied. We determined the involvement of afferent sensory neurons, calcitonin-gene-related peptide (CGRP), lipid peroxidation, and nitric oxide (NO) biosynthesis in gastroprotection of H₂S-releasing NaHS and CO-releasing tricarbonyldichlororuthenium(II) dimer (CORM-2) against aspirin-induced injury.

METHODS

Wistar rats with or without capsaicin-induced denervation of sensory neurons were pretreated with vehicle, CORM-2 (5 mg/kg intragastrically), or NaHS (5 mg/kg intragastrically) with or without capsazepine (5 mg/kg intragastrically) or N ^G-nitro-L-arginine (L-NNA, 20 mg/kg intraperitoneally). The areas of aspirin-induced lesions and gastric blood flow (GBF) were assessed by planimetry and laser flowmetry respectively. Gastric mucosal messenger RNA and/or protein expression of CGRP, heme oxygenase 1, inducible nitric oxide synthase, cyclooxygenase 2, interleukin-1β, glutathione peroxidase 1 (GPx-1), and superoxide dismutase was determined by real-time PCR or Western blot. Malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) content was determined by colorimetric assay.

RESULTS

Aspirin caused gastric lesions, decreased GBF, and raised MDA content, but pretreatment with NaHS and CORM-2 reduced these effects. Capsaicin-induced denervation or co-treatment with capsazepine reversed the gastroprotective and vasodilatory effects of NaHS but not those of CORM-2. L-NNA reversed NaHS-induced gastroprotection and partly reduced CORM-2-induced gastroprotection. NaHS and CORM-2 decreased MDA and 4-HNE content, restoring GPx-1 protein expression.

CONCLUSIONS

We conclude that H₂S- but not CO-mediated gastroprotection against aspirin-induced injury involves afferent sensory nerves and partly NO activity. NaHS and CORM-2 prevented aspirin-induced gastric mucosal lipid peroxidation via restoration of microcirculation and antioxidative GPx-1 protein expression.

Protective Effects of Genipin on Gastrointestinal Disorders

Genipin, an aglycone of geniposide, is a major component of gardeniae fructus, and has been used to treat jaundice, various inflammatory disorders, and liver disease, and has also been used as a natural cross-linking agent. The authors conducted several experiments to evaluate the protective effects of genipin on gastrointestinal disorders, such as, gastritis and gastric ulcers. Genipin showed inhibitory effects against HCl·ethanol-induced acute gastritis and indomethacin-induced gastric ulcers in rats and increased prostaglandin E₂ (PGE₂) in AGS gastric cancer cell. Genipin had significant effects on aggressive factors, acid-neutralization, and gastric secretion, and inhibited H⁺/K⁺-ATPase (a proton pump), which secretes gastric acid. The results obtained indicate that genipin has significant gastroprotective effects and might be useful for treating and preventing gastric lesions.

Interaction between endogenous carbon monoxide and hydrogen sulfide in the mechanism of gastroprotection against acute aspirin-induced gastric damage

Acetylsalicylic acid (ASA) is mainly recognized as painkiller or anti-inflammatory drug. However, ASA causes serious side effects towards gastrointestinal (GI) tract which limits its usefulness. Carbon monoxide (CO) and hydrogen sulfide (H₂S) have been described to act as important endogenous messengers and mediators of gastroprotection but whether they can interact in gastroprotection against acute ASA-induced gastric damage remains unknown. In this study male Wistar rats were pretreated with 1) vehicle (saline, i.g.), 2) tricarbonyldichlororuthenium (II) dimer (CORM-2, 5mg/kg i.g.), 3) sodium hydrosulfide (NaHS, 5mg/kg i.g.), 4) zinc protoporphyrin (ZnPP, 10mg/kg i.p.), 5) D,L-propargylglycine (PAG, 30mg/kg i.g.), 6) ZnPP combined with NaHS, 7) PAG combined with CORM-2 or 8) 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10mg/kg i.p.) combined with CORM-2 or NaHS and 30min later ASA was administered i.g. in a single dose of 125mg/kg. After 1h, gastric blood flow (GBF) was determined by H₂ gas clearance technique and gastric lesions were assessed by planimetry and histology. CO content in gastric mucosa and COHb concentration in blood were determined by gas chromatography and H₂S production was assessed in gastric mucosa using methylene blue method. Protein and/or mRNA expression for cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3-MST), heme oxygenase (HO)-1, HO-2, hypoxia inducible factor-alpha (HIF)-1α, nuclear factor (erythroid-derived 2)-like 2 (Nrf-2), cyclooxygenase (COX)-1 and COX-2, inducible nitric oxide synthase (iNOS) and interleukin (IL)-1β were determined by Western blot or real-time PCR, respectively. ASA caused hemorrhagic gastric mucosal damage and significantly decreased GBF, H₂S production, CO content, mRNA or protein expression for CSE, 3-MST, HO-2 and increased mRNA and/or protein expression for CBS, HO-1, Nrf-2, HIF-1α, iNOS, IL-1β, COX-2 in gastric mucosa and COHb concentration in blood. Pretreatment with CORM-2 or NaHS but not with PAG decreased ASA-damage and increased GBF. ZnPP reversed protective and hyperemic effect of NaHS but PAG failed to affect CORM-2-induced gastroprotection. CORM-2 elevated CO content, mRNA or protein expression for HO-1, Nrf-2, and decreased expression of CBS, HIF-1α, COX-2, IL-1β, iNOS, the H₂S production in gastric mucosa and COHb concentration in blood. NaHS raised mRNA or protein expression for CSE, COX-1 and decreased mRNA expression for IL-1β and COHb level in blood. We conclude that CO is involved in gastroprotection induced by H₂S while beneficial protective action of CO released from CORM-2 in gastric mucosa seems to be H₂S-independent. In contrast to H₂S, CO ameliorates hypoxia, regulates Nrf-2 expression but similarly to H₂S acts on sGC-dependent manner to restore gastric microcirculation and exhibit anti-inflammatory activity in gastric mucosa compromised by ASA.

Gastroprotective Activities of Sennoside A and Sennoside B via the Up-Regulation of Prostaglandin E2 and the Inhibition of H(+)/K(+)-ATPase

Sennoside A (erythro) and sennoside B (threo) are dianthrone glycosides and diastereomers. We investigated their abilities to prevent the gastric lesions associated with diseases, such as, gastritis and gastric ulcer. To elucidate their gastroprotective effects, the inhibitions of HCl•EtOH-induced gastritis and indomethacin-induced gastric ulcers were assessed in rats. It was observed that both sennoside A and sennoside B increased prostaglandin E₂ (PGE₂) levels and inhibited H⁺/K⁺-ATPase (proton pump). In a rat model, both compounds reduced gastric juice, total acidity and increased pH, indicating that proton pump inhibition reduces gastric acid secretion. Furthermore, sennoside A and B increased PGE₂ in a concentration-dependent manner. In a gastric emptying and intestinal transporting rate experiment, both sennoside A and sennoside B accelerated motility. Our results thus suggest that sennoside A and sennoside B possess significant gastroprotective activities and they might be useful for the treatment of gastric disease.

Effect of rebamipide on gastric bleeding and ulcerogenic responses induced by aspirin plus clopidogrel under stimulation of acid secretion in rats

BACKGROUND AND AIM

We examined the prophylactic effect of rebamipide on gastric bleeding induced by the perfusion of aspirin (acetylsalicylic acid [ASA]) plus clopidogrel under the stimulation of acid secretion in rats.

METHODS

Under urethane anesthesia, acid secretion was stimulated by the i.v. infusion of histamine (8 mg/kg/h), and the stomach was perfused with 25 mmol/L ASA at a rate of 0.4 mL/min. Gastric bleeding was evaluated as the concentration of hemoglobin in the perfusate. Clopidogrel (30 mg/kg) was given p.o. 24 h before the perfusion. Rebamipide (3-30 mg/kg) or other antiulcer drugs were given i.d. before the ASA perfusion.

RESULTS

Slight gastric bleeding or damage was observed with the perfusion of ASA under the stimulation of acid secretion, whereas these responses were significantly increased in the presence of clopidogrel. Both omeprazole and famotidine inhibited acid secretion and prevented these responses to ASA plus clopidogrel. Rebamipide had no effect on acid secretion, but dose-dependently prevented gastric bleeding in response to ASA plus clopidogrel, with the degree of inhibition being almost equivalent to that of the antisecretory drugs, and the same effects were obtained with the gastroprotective drugs, irsogladine and teprenone. These agents also reduced the severity of gastric lesions, although the effects were less than those of the antisecretory drugs.

CONCLUSIONS

These results suggest that the antiplatelet drug, clopidogrel, increases gastric bleeding induced by ASA under the stimulation of acid secretion, and the gastroprotective drug, rebamipide, is effective in preventing the gastric bleeding induced under such conditions, similar to antisecretory drugs.

Comparative effects of the anti-platelet drugs, clopidogrel, ticlopidine, and cilostazol on aspirin-induced gastric bleeding and damage in rats

AIMS

The present study compared the effects of frequently used anti-platelet drugs, such as clopidogrel, ticlopidine, and cilostazol, on the gastric bleeding and ulcerogenic responses induced by intraluminal perfusion with 25 mM aspirin acidified with 25 mM HCl (acidified ASA) in rats.

MAIN METHODS

The stomach was perfused with acidified ASA at a rate of 0.4 ml/min for 60 min under urethane anesthesia, and gastric bleeding was measured as the concentration of hemoglobin in the luminal perfusate, which was collected every 15 min. Clopidogrel (10-100mg/kg), ticlopidine (10-300 mg/kg), or cilostazol (3-30 mg/kg) was given p.o. 24h or 90 min before the perfusion of acidified ASA, respectively.

KEY FINDINGS

Perfusion of the stomach with acidified ASA alone led to slight bleeding and lesions in the stomach. The pretreatment with clopidogrel, even though it did not cause bleeding or damage by itself, dose-dependently increased the gastric bleeding and ulcerogenic responses induced by acidified ASA. Ticlopidine also aggravated the severity of damage by increasing gastric bleeding, and the effects of ticlopidine at 300 mg/kg were equivalent to those of clopidogrel at 100mg/kg. In contrast, cilostazol dose-dependently decreased gastric bleeding and damage in response to acidified ASA.

SIGNIFICANCE

These results demonstrated that clopidogrel and ticlopidine, P2Y12 receptor inhibitors, increased gastric bleeding and ulcerogenic responses to acidified ASA, to the same extent, while cilostazol, a phosphodiesterase III inhibitor, suppressed these responses. Therefore, cilostazol may be safely used in dual anti-platelet therapy combined with ASA, without increasing the risk of gastric bleeding.

New method of inducing intestinal lesions in rats by intraduodenal administration of aspirin

BACKGROUND AND AIMS

Enteroscopic observation has clearly demonstrated that non-steroidal anti-inflammatory drugs/low-dose aspirin (usually enteric-coated) induces hemorrhagic lesions, including ulcers and bleeding, in the small intestine of patients at a high incidence. Such intestinal lesions induced by NSAIDs have been confirmed in animal experiments. With aspirin, however, it has long been believed that it is difficult to induce any damage in the intestinal mucosa of laboratory animals. Therefore, we established a new method of inducing intestinal hemorrhagic lesions in rats by injecting aspirin into the proximal duodenum.

METHODS

Under ether anesthesia, aspirin (50-200 mg/body), suspended in 2% methylcellulose (with or without 0.1 N HCl), was injected into the proximal duodenum of normally fed or 20-h non-fed rats (male Sprague-Dawley, 9 weeks old). At 1 h after treatment, the animals were killed with ether and the entire small intestine was removed for histological examination. In some experiments, 1% Evans blue was injected (i.v.) into the rats 1 h after aspirin treatment to visualize the lesions. An image analyzer determined the total area of the intestinal lesions. Oral proton pump inhibitors and histamine H(2)-receptor blockers were given 1 h before aspirin injection. 16,16-dimethyl prostaglandin E(2) (dmPGE(2)) was given s.c. 30 min before aspirin injection.

RESULTS

Aspirin alone clearly induced severe lesions (including bleeding and ulcers) mainly in the jejunum at 100% incidence. Total score of lesions per rat obtained by histological examination was similar to the damaged area quantified with the dye method. Dose-related induction of lesions by aspirin was confirmed both by the histological and dye methods. The irritable effect of aspirin suspended in 0.1 N HCl solution was the same as that of aspirin alone; 0.1 N HCl alone induced only minor lesions in the intestine. Both proton pump inhibitors and histamine H(2)-receptor blockers, at doses that inhibit gastric acid secretion, had no or little effect on aspirin-induced intestinal lesions. Pretreatment with dmPGE(2) (3, 10, 30 microg/kg) showed significant prevention of both aspirin- and HCl/aspirin-induced intestinal lesions.

CONCLUSION

This new aspirin lesion model will be useful for screening defensive drugs against aspirin-induced intestinal lesions and to elucidate the underlying mechanism.

Effects of allyl isothiocyanate from horseradish on several experimental gastric lesions in rats

Allyl isothiocyanate is well known to be a principal pungent constituent of horseradish and an agonist for transient receptor potential (TRP) A1. Ally isothiocyanate markedly inhibited the formation of gastric lesions induced by ethanol (1.5 ml/rat, p.o.), 0.6 M HCl (1.5 ml/rat, p.o.), 1% ammonia (1.5 ml/rat, p.o.), and aspirin (150 mg/kg, p.o.) (ED(50)=1.6, 2.2, 1.7, ca. 6.5 mg/kg, p.o.). It also significantly inhibited the formation of gastric lesions induced by indomethacin (20 mg/kg, p.o.), though the inhibition was ca. 60% at a high dose (40 mg/kg, p.o.). Furthermore, several synthetic isothiocyanate compounds also significantly inhibited ethanol and indomethacin-induced gastric lesions. Whereas, TRPV1 agonists, capsaicin and piperine, inhibited gastric lesions induced by ethanol, 1% ammonia, and aspirin, but had less of an effect on 0.6 M HCl-induced gastric lesions. With regard to mode of action, the protective effects of ally isothiocyanate on ethanol-induced gastric lesions were attenuated by pretreatment with indomethacin, but not with N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME), or ruthenium red. Pretreatment with indomethacin reduced the protective effects of piperine, and L-NAME reduced the effects of capsaicin and omeprazole. Furthermore, ruthenium red reduced the effects of capsaicin, piperine, and omeprazole. These findings suggest that endogenous prostaglandins play an important role in the protective effect of allyl isothiocyanate in ethanol-induced gastric lesions different from capsaicin, piperine, and omeprazole.

alpha-Amino acid derivatives as proton pump inhibitors and potent anti-ulcer agents

In a program to identify new anti-ulcer compounds, a series of N-acyl derivatives of alpha-amino acids were screened for their in vitro H(+)/K(+) ATPase inhibitory activity, and in vivo efficacy in Pylorus ligation model. 3D-QSAR studies were carried out and a representative compound 13 was studied for the nature of its proton pump inhibition.

Essential role of pepsin in pathogenesis of acid reflux esophagitis in rats

Pepsin, a protease activated by gastric acid, is a component of the refluxate, yet the role of pepsin in the pathogenesis of reflux esophagitis has not been well studied. In the present study, we examined the effect of pepstatin, a specific inhibitor of pepsin, on acid reflux esophagitis. Acid reflux esophagitis was induced in rats by ligating both the pylorus and the forestomach for 3 or 4 hr. Pepstatin, ecabet Na (the anti-ulcer drug), and L-glutamine were administered intragastrically after the ligation. Pepstatin or ecabet Na, given intragastrically, significantly prevented esophageal lesions, even though they did not affect basal acid secretion in pylorus-ligated rats. Pepstatin significantly inhibited pepsin activity in vivo and in vitro, while ecabet Na inhibited this activity in vitro. By contrast, L-glutamine given intragastrically aggravated the lesions in a dose-dependent manner, but even in the presence of L-glutamine the development of esophageal lesions was totally prevented by coadministration of pepstatin or ecabet Na. L-Glutamine increased the pH of gastric contents to approximately 2.0, the optimal pH for the proteolytic activity of pepsin in vitro. In addition, intragastric administration of exogenous pepsin worsened the severity of esophageal damage. These results suggest that pepstatin is highly effective against acid reflux esophagitis, without influencing acid secretion, while L-glutamine aggravated these lesions by increasing the pepsin activity by shifting the intraluminal pH to the optimal pH range for proteolytic action. It is assumed that pepsin plays a major pathogenic role in the development of acid reflux esophagitis.

[An overview of acetic acid ulcer models and their utility for drug screening]

Since Takagi et al. reported an experimental chronic gastric ulcer model [acetic acid ulcers induced by submucosal injection of acetic acid (Type 1)], we further modified the methodology and subsequently devised three more models. The second model involves inducing ulcers by serosal application of an acetic acid solution (Type 2) and the third model achieves ulcer induction by intragastric application of an acetic acid solution (Type 3). The forth model was modification of the third model by giving the acetic acid solution and the same volume of air to make one ulcer in the stomach (Type 4). In general, animals accepted the procedures without problems and no undesirable effects were noticed. More importantly, this experimental animal model allows production of ulcers that highly resemble human ulcers in terms of both pathology and healing. Indeed, relapse is even endoscopically observed for 360 days after ulceration. The ulcers produced not only respond well to various anti-ulcer medications, such as antisecretory and mucosal protective drugs and growth factors, but also demonstrate appropriate responses to ulcerogenic agents such as NSAIDs. In addition, we have recently demonstrated that H. pylori infection resulted in delayed ulcer healing and recurrence of healed acetic acid ulcers induced in Mongolian gerbils. The present article gives a brief summary of the ulcer history before establishment of acetic acid ulcers and characteristic features of acetic acid ulcer, including both their merits and shortcomings.

Gastroprotective effects of phenylpropanoids from the rhizomes of Alpinia galanga in rats: structural requirements and mode of action

The effects of 1'S-1'-acetoxychavicol acetate and related phenylpropanoids isolated from the rhizomes of Alpinia galanga on ethanol-induced gastric lesions in rats were examined. Among them, 1'S-1'-acetoxychavicol acetate and 1'S-1'-acetoxyeugenol acetate markedly inhibited the ethanol-induced gastric mucosal lesions (ED(50)=0.61 and ca. 0.90 mg/kg). In addition, 1'S-1'-acetoxychavicol acetate inhibited the lesions induced by 0.6 M HCl (ED(50)=0.73 mg/kg) and aspirin (ED(50)=0.69 mg/kg) but it did not show a significant effect on indomethacin-induced gastric lesions and acid output in pylorus-ligated rats at doses of 0.5-5.0 mg/kg. From the gastroprotective effects of various related compounds, the 1'-acetoxyl group of 1'S-1'-acetoxychavicol acetate and 1'S-1'-acetoxyeugenol acetate was found to be essential for their strong activity. With regard to the mode of action, the gastroprotective effects of 1'S-1'-acetoxychavicol acetate were attenuated by pretreatment with indomethacin and N-ethylmaleimide, and 1'S-1'-acetoxychavicol acetate significantly increased the glutathione levels of gastric mucosa in rats. These findings suggest that endogenous prostaglandins and sulfhydryl compounds are involved in the protective effect of 1'S-1'-acetoxychavicol acetate.

Protective effects of polygodial on gastric mucosal lesions induced by necrotizing agents in rats and the possible mechanisms of action

The effects of polygodial isolated from the leaves of Tasmannia lanceolata on necrotizing agents-induced gastric lesions in rats were compared with capsaicin. Polygodial markedly inhibited the gastric mucosal lesions induced by several necrotizing agents, such as ethanol (ED(50)=0.029 mg/kg, p.o.), 0.6 M HCl (ED(50)=0.26 mg/kg, p.o.), and aspirin (ED(50)=0.38 mg/kg, p.o.), and partly inhibited the gastric mucosal lesions induced by indomethacin, but showed no significant effect on acid output in pylorus-ligated rats at doses of 0.05-0.5 mg/kg. The gastroprotection of polygodial was attenuated by pretreatment with indomethacin (10 mg/kg, s.c.), N(G)-nitro-L-arginine methyl ester (70 mg/kg, i.p.), N-ethylmaleimide (10 mg/kg, s.c.) and ruthenium red (3.5 mg/kg, s.c.). Polygodial (0.2 mg/kg, p.o.) increased the amount of reduced glutathione in gastric mucosa of ethanol-treated group. These results suggested that endogenous prostaglandins, nitric oxide, sulfhydryl compounds and vanilloid receptor-mediated effects are involved in the protective effect of polygodial.

Effect of butanol fraction of Panax ginseng head on gastric lesion and ulcer

From our previous result that Panax ginseng head extract had inhibition of gastric damages, the extract was fractionated. Among the hexane, chloroform, butanol and water fractions, butanol fraction showed the most potent inhibition of HCl.ethanol-induced gastric lesion, aspirin-induced gastric ulcer, acetic acid-induced ulcer and Shay ulcer. Butanol fraction showed significant increase in mucin secretion, and inhibited malondialdehyde (MDA) and H+/ K+ATPase activity in the stomach. This results indicate that the effectiveness of the fraction on gastric damages might be related to inhibition of acid secretion, increment of mucin secretion and antioxidant property.

Effects of Opuntia ficus-indica var. Saboten stem on gastric damages in rats

The effects of the dried stem powder of Opuntia ficus-indica var. saboten (OF-s) were investigated on gastric lesion and ulcer models in rats. It showed significant inhibition in HCl ethanol-induced gastric lesion at the doses of 200 and 600 mg/kg p.o. and in HCl.aspirin-induced gastric lesion at 600 mg/kg p.o. OF-s also showed significant inhibition in indomethacin-induced gastric lesion at the doses of 200 and 600 mg/kg, p.o. However, it did not affect both the aspirin-induced and Shay ulcers in rats. It also did not affect gastric juice secretion, acid output and pH. These data indicate that OF-s only possesses pronounced inhibitory action on gastric lesion without antiulcer activity in rats.

A new gastric ulcer model induced by ischemia-reperfusion in the rat: role of leukocytes on ulceration in rat stomach

A new model of gastric ulcer involving damage to the muscularis mucosae was developed by clamping the celiac artery in rat to induce ischemia-reperfusion (I-R) injury. Although erosions with falling off of the gastric mucosa were observed immediately, 24 and 36 hours after the I-R, gastric ulcers involving the injury of muscularis mucosae were observed in the area of gastric glands at 48 and 72 hours after initiation of injury. Administration of omeprazol, a proton pump inhibitor, or pentoxifylline, an anti-leukocyte drug, just after the initiation of injury significantly decreased the total area of ulcers at 72 hours. A combination of omeprazol and pentoxifylline was more effective than either drug alone. An anti-leukocyte adhesion molecule (anti-CD18 antibody) also showed significant inhibitory effect on the development of ulcers at 72 hours and the infiltration of leukocytes into both submucosa and mucosa. These results indicate that in our model, gastric acid together with leukocytes contribute to the development of ulcers following erosions. This model may be used to investigate the mechanisms of the development of gastric ulcer and evaluate antiulcer drugs in a preclinical setting.

Pharmacological profile of gastric mucosal protection by marmin and nobiletin from a traditional herbal medicine, Aurantii fructus immaturus

We studied the effects of marmin and nobiletin on the experimental acute gastric lesions, gastric transmucosal potential difference (PD) and gastric motor activity in rats and the contractions of isolated guinea pig ileum. Oral administration of marmin and nobiletin inhibited both the appearance of ethanol-induced gastric hemorrhagic lesions dose-dependently in a dose range of 10-50 mg/kg, with ED50 values for marmin and nobiletin being 17.2 and 8.0 mg/kg, respectively. However, marmin and nobiletin had minimal effects on aspirin-induced gastric lesions at a dose of 50 mg/kg, respectively. Marmin and nobiletin had no significant influence on the basal PD. Intragastrical administration of marmin and nobiletin at a dose of 25 mg/kg significantly prevented the PD reduction induced by ethanol. Both marmin and nobiletin given intragastrically at 25 mg/kg significantly inhibited gastric motor activity measured as intraluminal pressure recordings. Marmin and nobiletin exhibited concentration-dependent relaxations of contractions induced by acetylcholine, transmural electrical stimulation and histamine in isolated guinea pig ileum, respectively. These findings suggest that the anti-ulcer effects of marmin and nobiletin are ascribed primarily to the maintenance of the mucosal barrier integrity and inhibition of gastric motor activity and secondarily due to the prevention of the effects of endogenous acetylcholine and histamine.

Gastric motility and ischemic changes in occurrence of linear ulcer formation induced by restraint-water immersion stress in rat

The pathogenesis of linear ulceration induced by restraint water-immersion (RWI) was investigated in view of gastric motility and early ischemic changes. After three hours of restraint-water immersion stress, the cross-sectioned gastric body was prepared for light microscopy. Most lesions (90.8%) were present in the mucosal folds projecting toward the cavity. Wedge-shaped degeneration in the crest of the folds was recognized as an ischemic lesion followed by hemorrhagic ulceration. Compressed arterioles were frequently encountered in the muscularis mucosae and circular muscle. Generally, mucosal folds appear merely with the reduction of gastric content, and run along with the elevation of the circular muscle as an anatomical structure, becoming tall and steep after RWI. Marked enhancement of contraction, observed with a strain gauge force transducer, was induced by RWI. This enhancement was suppressed by papaverine HCl pretreatment in accordance with suppression of the fold-related mucosal lesion even after 150 mM HCl perfusion into the stomach. In conclusion, gastric motility appears to play an important role in the pathogenesis of linear ulceration by causing ischemic change along the folds.

Comparative evaluation of ulcer prevention efficacy of orally, rectally and sublingually administered omeprazole in three acute gastric ulcer models in rats

Ulcer prevention efficacy of orally, rectally and sublingually administered omeprazole was evaluated and compared using ulcer index and percentage inhibition of ulcerogenicity in three different acute gastric ulcer models viz, indomethacin, 0.6N HCl and aspirin (after pylorus ligation) induced ulcers in rats. The ulcer prevention efficacy after oral, rectal and sublingual administration were statistically significant (P < 0.01) in all the models. The differences in ulcer index and percentage inhibition of ulcerogenicity for rectal and sublingual administration were insignificant (P < 0.05) in indomethacin and HCl induced ulcers and were significant (P < 0.05) in aspirin induced ulcers. The ulcer prevention activity was significantly higher (P < 0.05) after rectal and sublingual routes when compared to oral administration in all three models evaluated. Results revealed a faster onset and higher extent of pharmacodynamic activity of omeprazole after rectal and sublingual administration.

Gastric hyperacidity and mucosal damage caused by hypothermia correlate with increase in GABA concentrations of the rat brain

The involvement of brain GABA mechanisms in acid secretion and maintenance of gastric mucosal integrity was studied in the anesthetized rat. Cold exposure lowered the rectal temperature and stimulated acid output in the anesthetized rat. The acid response to cold exposure was completely suppressed by surgical vagotomy. The substantial increase in brain GABA content evoked by pretreatment with aminooxyacetic acid (10 and 20 mg/kg s.c. x 3) significantly potentiated the gastric acid response to the cold exposure stress; suppression of the GABA content induced by semicarbazide (100 mg/kg s.c.) reduced the acid response to cold. Significant correlations were found between the brain GABA contents and the acid secretory activity and also between the GABA contents and the ulcer index of gastric lesions induced by the cold stress. These results indicate that hypothermia evoked by cold exposure stimulates gastric acid secretion and induces gastric lesions through central GABA mechanisms in the rat.

The affinity, selectivity and biological activity of telenzepine enantiomers

The binding of the enantiomers of telenzepine to muscarinic receptor subtypes present in guinea-pig cerebral cortex, myocardium and salivary glands has been examined. The (+) enantiomer is more potent in all assays and exhibits a greater selectivity than the (-) enantiomer for the different receptor subtypes. As a consequence, the enantiomeric potency ratio varies from ca. 400 (cortical 'M1' receptors) to ca. 50 (cardiac receptors). In functional assays in vitro in the rabbit vas deferens and rat atria, the affinity constants and enantiomeric potency ratios for the two isomers agree with those found for the appropriate muscarinic receptor subtype in binding assays. A high enantiomeric potency ratio, 180, is found in vivo for the ability of the telenzepine enantiomers to inhibit the production of lesions in the modified Shay rat preparation. The data are compatible with the blockade of M1 receptors by (+)-telenzepine being responsible for this action of telenzepine and would tend to exclude the possibility that the anti-ulcer action of telenzepine is mediated via a muscarinic or non-muscarinic action of the (-) enantiomer.

Time-course study of gastric damages in rats by anti-inflammatory drugs using a gastroscope and its quantification

Time-course studies on gastric damages in rats caused by nonsteroidal anti-inflammatory drugs (NSAIDs) were performed using a gastroscope, and the readings were quantified to obtain the Congestion-Hemorrhage Index (CHI) for evaluating the potencies of the damaging properties of NSAID. The correlation between CHI and Ulcer Index (UI), the quantified value obtained by the conventional methods, was highly significant at 6 and 24 hr after forced oral administration of NSAID. The peak CHIs of aspirin (300 mg/kg), indomethacin (60 mg/kg), mefenamic acid (300 mg/kg) and fenoprofen calcium (300 mg/kg) appeared approximately 24 hr after a single forced oral administration of drugs. Thus, it was suggested that an observation at 24 hr in addition to one at 6 to 7 hr might be necessary for the examination of damaged gastric mucosa. Under the present experimental conditions, fenoprofen calcium caused the greatest damages on gastric mucosa among the four NSAIDs. Mefenamic acid showed the least damaging potency on gastric mucosa, having a smaller CHI than that of aspirin. Indomethacin possessed a stronger damaging property than aspirin.

Antiulcer effect of (-)-cis-2,3-dihydro-3-(4-methylpiperazinylmethyl) -2-phenyl-1,5-benzothiazepin-4-(5H)-one hydrochloride (BTM-1086) in experimental animals

Effects of (-) cis-2,3-dihydro-3-(4-methylpiperazinylmethyl)-2-phenyl-1,5-benz othiazepin-4-(5H ) -one hydrochloride (BTM-1086) on various experimental gastric and duodenal ulcers were studied in rats. In the pylorus-ligated ulcer, restraint and water immersion stress ulcer, and drug-induced ulcer (indomethacin, aspirin, reserpine, serotonin, cysteamine), BTM-1086 prevented the development of ulcer at a dose of 0.1 to 1 mg/kg, p.o., but only weakly inhibited the histamine-induced gastric ulcer. The inhibitory activities of BTM-1086 were significantly higher than those of atropine sulfate. In the healing experiment with the acetic acid-induced stomach ulcer, BTM-1086 (1 mg/kg/day, p.o., X 14) showed a significant healing effect, which was higher than that of propantheline bromide. BTM-1086 at a dose of 0.2 mg/kg, i.d., remarkably inhibited the gastric secretion 6 hr after pylorus ligation. The aspirin-induced reductions of the total acid and K+ as well as the increments of the volume and Na+ in the gastric secretion were prevented dose-dependently by pretreatment with BTM-1086.

Biochemical and pharmacological analysis of 2-[(2-dimethylaminobenzyl)sulfinyl] benzimidazole (NC-1300), a new proton pump inhibitor

Biochemical and pharmacological properties of a newly synthesized compound, 2-[(2-dimethylaminobenzyl)sulfinyl] benzimidazole (NC-1300), were studied. NC-1300, at pH 6.0, potently inhibited the activity of H+ K+ ATPase in the rabbit gastric mucosa, thereby classifying it as a proton pump inhibitor. The inhibitory efficacy of NC-1300 on the pump was much the same as that seen with omeprazole. NC-1300 had no effect on acetylcholine-stimulated ileum contraction in guinea pigs at 10(-5) M, but it non-competitively inhibited the contraction at 10(-4) M. NC-1300 had no effect on histamine-stimulated atrial beating frequency in guinea pigs at 10(-4) or 10(-5) M. NC-1300, given either intraduodenally or orally, had a potent and long-lasting (more than 24 hr) inhibitory effect on gastric secretion in pylorus-ligated rats. Pretreatment with NC-1300 dose-dependently protected the gastric mucosa from damage induced by pylorus ligation, water-immersion stress, aspirin, and indomethacin, and the duodenal mucosa from damage induced by mepirizole in rats. We conclude that the antisecretory activity of NC-1300 appears to be mainly related to an inhibition of H+ K+ ATPase, while its antigastric and antiduodenal lesion activities are primarily related to an antisecretory effect.

Effects of 15(R)-15-methyl prostaglandin E2 (arbaprostil) on gastric secretion and various gastric lesions induced in rats

We studied the effects of 15(R)-15-methyl prostaglandin E2 (arbaprostil) on gastric secretion and various acute and chronic gastric lesions produced in rats. Arbaprostil significantly inhibited gastric secretion in 4 hr-pylorus-ligated preparations when given intraduodenally in a dose of 30 or 100 micrograms/kg. The agent, however, significantly stimulated gastric secretion of rats with either a ligated or intact pylorus when given orally in doses of 3-100 micrograms/kg. Orally administered arbaprostil dose-dependently prevented the development of HCI-ethanol-, histamine-, water-immersion stress-, or indomethacin-induced gastric erosions. Intraduodenally administered arbaprostil also dose-dependently prevented the development of aspirin-induced gastric erosions in pylorus-ligated rats. Arbaprostil, given orally in doses of 1-100 micrograms/kg twice daily for 2 weeks, had little or no effect on the healing of acetic acid-induced gastric ulcers. However, oral administration of the agent in a dose of 3 or 10 micrograms/kg twice daily for 4 weeks significantly accelerated the healing of acetic acid-induced gastric ulcers. The increase in doses up to 100 micrograms/kg twice daily for 4 weeks had no effect on ulcer healing. These results indicate that arbaprostil, at either antisecretory or even acid stimulating doses, is effective in preventing the development of acute gastric erosions and in accelerating the healing of chronic gastric ulcers.

Effects of exogenous administration of female sex hormones on gastric secretion and ulcer formation in the rat

The effects of progesterone 10 mg/kg, estrogen 5 mg/kg and a combination of both at half these doses were studied in rats. Ulcers were induced in rats by means of various experimental models: drug-induced ulcers (aspirin or indomethacin), stress ulcer and Shay rat. The female sex hormones were found to have significant antiulcer activity in almost all the models. However, they did not affect the acidity or volume of gastric secretion in Shay's pyloric ligation model. As a result their antiulcer activity could not be explained by the effects on gastric acidity but by effects on other factors which may include enhanced mucus activity, or increase in parietal cells activity and maintenance of mucus integrity.

Effects of FPL-52694, a new mast cell stabilizer, on gastric secretion and various acute gastric lesions in rats

Oral FPL-52694 [5-(2-hydroxypropoxy)-8-propyl-4-oxo-4H-1-benzopyran-2-carboxylic acid Na], a new mast cell stabilizer, dose-dependently inhibited gastric acid secretion but increased the volume and pepsin output in pylorus-ligated rats. Intraduodenal FPL-52694 significantly inhibited all of the volume, acidity, acid output and pepsin output. Concerning the acidity, oral administration of the agent showed much more potent inhibition than intraduodenal administration. Oral FPL-52694 markedly inhibited the development of pylorus-ligated ulcers, water-immersion stress- and aspirin-induced gastric erosions and moderately inhibited the formation of reserpine-induced gastric erosions in rats. Intraduodenal FPL-52694 also inhibited pylorus-ligated ulcers whereas it had no effect on aspirin-induced gastric erosions. Histamine-induced gastric erosions were not affected by oral FPL-52694. These effects of FPL-52694 were almost the same as those of cimetidine, except that cimetidine tended to inhibit histamine-induced gastric erosions. Although the precise mechanism of action of FPL-52694 remains unknown, oral FPL-52694 appears to be a promising agent for the treatment of peptic ulcers.

Effects of a proton pump inhibitor, omeprazole, on gastric secretion and gastric and duodenal ulcers or erosions in rats

The effects of omeprazole, a proton pump inhibitor, on gastric secretion and gastric or duodenal ulcers or erosions in rats were studied. Omeprazole, given intraduodenally, dose-dependently inhibited the gastric secretion (volume, acid and pepsin output) of pylorus-ligated rats. The antisecretory activity of omeprazole at 100 mg/kg persisted for 14 hr after treatment. Acutely induced gastric ulcers or erosions such as Shay ulcers, water-immersion stress-, indomethacin-, aspirin-, or prednisolone-induced erosions were all markedly inhibited by oral or intraduodenal administration of 10-100 mg/kg of omeprazole. The development of duodenal ulcers and gastric erosions caused by mepirizole was also potently inhibited by omeprazole at 3-10 mg/kg given orally. Repeated administration of omeprazole, 200 mg/kg/day in two divided doses for 14 days, significantly accelerated the spontaneous healing of acetic acid-induced gastric ulcers. The mechanism by which omeprazole inhibits the development of acute ulcers and accelerates healing of preexisting ulcers appears to be mainly due to its potent and long-lasting antisecretory activity. The antisecretory and antiulcer activities of omeprazole are equal to or exceed those of cimetidine, both in the maximum inhibitory response and ED50 values.

Effects of an antiulcer drug, sucralfate (a basic aluminum salt of sulfated disaccharide), on experimental gastric lesions and gastric secretion in rats

The effects of oral sucralfate, a basic aluminum salt of sulfated disaccharide, on various experimental gastric lesions and on gastric secretion were studied in rats. Sucralfate at 300 mg/kg potently inhibited the development of Shay ulcers and indomethacin- and aspirin-induced erosions. The drug at 1000 mg/kg also potently inhibited histamine-induced erosions. Water-immersion stress-induced erosions were inhibited with 1000 mg/kg of the drug, but the degree of inhibition was weaker than that seen in other types of erosion formation. Sucralfate at 1000 mg/kg given twice daily for 14 days significantly accelerated the spontaneous healing of acetic acid-induced ulcers. Sucralfate at over 300 mg/kg tended to increase the volume of gastric juice but had an insignificant effect on acid and pepsin output of pylorus-ligated rats. As a whole, the effects of sucralfate on experimental gastric lesions appear to be much more potent than Maalox, propantheline bromide, and cimetidine. The mechanism of action of sucralfate remains to be determined.

Effects of cholestyramine and synthetic hydrotalcite on acute gastric or intestinal lesion formation in rats and dogs

Cholestyramine, a bile-binding agent, markedly inhibited the development of gastric lesions induced by water-immersion stress in rats and of gastric and intestinal lesions induced by indomethacin in rats and dogs with an intact pylorus. However, cholestyramine had no effect on gastric lesions induced by stress in pylorus-ligated rats and on aspirin-induced gastric lesions in rats and dogs with or without pylorus ligation. Hydrotalcite, a potent antacid, significantly inhibited the gastric lesions induced by stress and aspirin in rats and dogs with or without pylorus ligation. Hydrotalcite also inhibited the gastric lesions induced by a single administration of indomethacin in rats with an intact pylorus. In contrast, the agent had no effect on gastric and intestinal lesions induced by repeated administration of indomethacin to rats and dogs with an intact pylorus. These results suggest that while bile probably plays an important role in the pathogenesis of stress-induced gastric lesions and of indomethacin-induced gastric and intestinal lesions, bile does not appear to play a role in the pathogenesis of aspirin-induced gastric lesions.

Strain differences in aspirin-induced gastric ulceration in rats

We found that there are strain differences in aspirin-induced ulceration in pylorus-ligated rats; the ulcer indices varied, from high to low, in the following order: Donryu greater than Sprague-Dawley greater than Wistar. Several experiments including analysis of gastric contents or ionic flux, determination of serum aspirin esterase activity, absorption of aspirin from the stomach, prothrombin time and hexosamine content in gastric mucosa and juice were performed to elucidate the origin of the differences. A significantly higher acid output in Donryu rats, and higher hexosamine content in the gastric mucosa of Wistar rats were noted. However, it appears unlikely that these factors only contribute to the marked strain difference in aspirin-induced ulcers. The possible different sensitivity of gastric mucosal cell itself to aspirin must be considered.

Inhibitors of gastric lesions in the rat

The production by stress of gastric lesions in rats was inhibited by metiamide and by mepyramine. Lesions induced by indomethacin treatment were inhibited by mepyramine but not by metiamide. Those induced by aspirin treatment in pylorus-ligated rats were not affected by either antihistamine drug. Oral glutamine inhibited lesion production in all three systems whereas aspirin orally markedly potentiated it. Sodium salicylate inhibited both indomethacin-induced lesions and those produced by aspirin in pylorus-ligated rats. On the other hand, copper salicylate inhibited stress-induced lesions and it, like copper aspirinate, also markedly reduced the extent of lesions produced by aspirin. On the basis of these results, stress-induced lesion production offers a suitable animal model for testing anti-ulcer drugs as it is, like most human gastric ulcers, inhibited by H2-receptor inhibitors like metiamide.

Influence of surgical sympathectomy on gastric secretion and ulceration in rats

The influences of sympathectomy on gastrointestinal mucosa, gastric secretion, acute or chronic gastric ulcers were studied in rats. Uncer ether anesthesia, sympathectomy was performed by surgical removal of the celiac ganglion. Surgical sympathectomy per se produced no pathological changes in the gastrointestinal tract as determined by macroscopical observation 3, 10 or 20 days after operation. The volume of gastric juice and pepsin output were not influenced by the sympathectomy but gastric acid output was significantly increased in pylorus-ligated rats. The sympathectomy worsened the stress- and the indomethacin-induced ulcer and delayed the healing of chronic gastric ulcers a little but not significantly, and had no deteriorative influence on the reserpine-induced ulcers. In contrast, Shay ulcers, aspirin- or secrotonin-induced ulcers were significantly aggravated by sympathectomy. The loss of H+ ions and gain of Na+ ions in the gastric juice of pylorus-ligated and aspirin-treated rats were not affected by sympathectomy.

Effects of cimetidine, a histamine H2-receptor antagonist, on various experimental gastric and duodenal ulcers

The effects of cimetidine, a new histamine H2-receptor antagonist, on the development of experimental gastric and duodenal ulcers were studied. It was found that either by the oral, intraduodenal, or intraperitoneal route this agent had a marked inhibitory activity on stress-, aspirin-, indomethacin-, or histamine-induced gastric ulcers in rats and guinea pigs. The effects of cimetidine on stress-, aspirin-, and indomethacin-induced gastric ulcers were dose-dependent in many cases. Pylorus-ligation uclers, reserpine- or serotonin-induced gastric ulcers were little influenced by cimetidine. Duodenal ulcers induced by continuous infusion of carbachol-histamine were significantly inhibited by a simultaneous infusion of cimetidine. An analysis of gastric contents in pylorus-ligated rats after stressing indicated a decreased volume and acid output as the result of intraduodenal cimetidine treatment. In contrast, cimetidine exerted little influence on gastric secretion in rats treated with aspirin or in guinea pigs treated with histamine. Thus, the mechanism of action of cimetidine in preventing gastric or duodenal ulcers is likely to occur by suppression of gastric secretory function in a duodenal ulcer model but by suppression of other unknown ulcerogenic factors in gastric ulcer models.

Effects of L-glutamine on acetylsalycylic acid induced gastric lesions and acid back diffusion in dogs

Effects of L-glutamine on acetylsalicylic acid (ASA)-induced gastric mucosal lesions were studied in mongrel dogs. It was confirmed that when oral ASA at 1.0 or 2.0 g per dog is given in two divided doses, there is severe and consistent dose-dependent mucosal damage in the glandular portion of the stomach in fasted dogs. However, when L-glutamine 2.0 or 4.0 g per dog in two divided doses is given concomitantly with ASA 2.0 g per dog orally, the gastric irritation is significantly inhibited. Instillation of 20 mM of ASA in 100 mM HCl solution into the Heidenhain pouch of Beagle dogs produced a significant loss of H+ from the pouch and a gain of Na+ in the lumen compared with ASA-free controls. When L-glutamine (100 mM) was given concomitantly with ASA (20 mM) into the pouch, changes of electrolyte fluxes in response to ASA alone were significantly suppressed. However, 50 mM of L-glutamine had no appreciable effect on acid back diffusion caused by ASA 20 mM. The amino acid itself had little effect on the ionic movement in the pouch. Gross bleeding from the pouch treated with ASA was never observed with the concomitant dosing of ASA and L-glutamine 50 or 100 mM.

Influence of pregnancy on the development of various gastric lesions in rats

The influence of pregnancy, and to some extent lactation, on various gastric lesions in rats were studied. Shay ulceration and gastric lesions induced by cold-restraint stress and ulcerogenic agents, such as acetylsalicylic acid (ASA), reserpine, or epinephrine, in rats were significantly aggravated by pregnancy (day 20 of pregnancy). Gastric hypersecretion, which was observed during pregnancy in pylorus ligation preparation, appears to contribute to the mechanism of aggravation of gastric lesions. ASA induced a marked back-diffusion of acid in pregnant rats which might resulted in the aggravation of ASA-induced gastric lesions. In contrast, histamine-induced gastric lesions were markedly inhibited according according to the progress of pregnancy but after 10 days' lactation returned to the level seen in nonpregnant rats. The histaminase inhibitor aminoguanidine strongly aggravated the histamine-induced gastric lesions in pregnant rats as compared with the non-pregnant ones.

Effects of carbenoxolone Na on acute and chronic gastric ulcer models in experimental animals

Effects of carbenoxolone Na on acute or chronic types of gastric lesions or ulcer models produced in rats, guinea pigs, or dogs were studied. Carbenoxolone Na, given either orally or intraperitoneally, produced a significant inhibition of stress-induced gastric lesions in intact or in pylorus-ligated rats. Acetylsalicylic acid (ASA)-induced or serotonin-induced gastric lesions in rats were also inhibited significantly by pretreatment with the drug. However, carbenoxolone Na did not affect the development of Shay ulceration in rats even though the peptic activity in gastric juices was markedly reduced by the drug. Histamine-induced gastric lesions in guinea pigs were not prevented by pretreatment with carbenoxolone Na. Although carbenoxolone Na, given for 10-20 days, did not promote the healing of stress-induced gastric lesions and acetic acid gastric jlcers in rats, it significantly accelerated the healing of chronic gastric ulcer produced in dogs by 3 weeks' treatment. Carbenoxolone Na prevented the acid back-diffusion caused by ASA without any influence on Na+ efflux in pylorus-ligated rats.

Effects of L-glutamine of acetylsalicylic acid or taurocholic acid-induced gastric lesions and secretory changes in pylorus-ligated rats under normal or stress conditions

An oral dosing of either acetylsalicylic acid (ASA) or taurocholic acid (TCA) to pylorus-ligated rats subjected to water-immersion stress produced severe damage to the gastric musoca in contrast to the irritation observed in non-stressed ones. The irritative activity of ASA or TCA on gastric mucosa under stress was dose-dependent. Stress itself (23 degrees C, 7 hr) did not induce any appreciable changes in gastric mucosa under stress wasic mucosa of rats. L-glutamine, given together with SAS or TCA, significantly prevented the potentiated development of SAS- or TCA-induced gastric lesions in stressed rats. L-glutamine also prevented in varying degrees the reduction of acid and increment of Na+ ion in gastric juice accumulated in stressed rats in response to ASA or TCA.

Influence of a new antiulcer agent, ammonium 7-oxobicyclo (2, 2, 1) hept-5-ene-3-carbamoyl-2-carboxylate (KF-392) on gastric lesions and gastric mucosal barrier in rats

Antiulcer effects of KF-392 were studied in several experimental gastric ulcer models in rats. It was found that KF-392 given orally at 1.0 to 5.0 mg/kg had a marked suppression on the developments of Shay ulcer as well as the aspirin-, stress-, and reserpine-induced gastric lesions. The influence of KF-392 on gastric mucosal barrier was also studied. A back diffusion of H+ into the gastric mucosa and a fall of transmucosal potential difference were induced with KF-392 given orally at the above mentioned doses. KF-392 given s.c. at 5.0 mg/kg showed no inhibition of Shay ulcer and no induction of back diffusion of H+ into the gastric mucosa.

Inhibitory effect of L-glutamine on gastric irritation and back diffusion of gastric acid in response to aspirin in the rat

L-Glutamine given orally at 750 mg/kg significantly reduced the formation of gastric mucosal lesions induced by aspirin at 100 mg/kg at 1, 3, and 7 hours in pylorus-ligated rats. L-Glutamine markedly inhibited the loss of H+ and a corresponding increment of Na+ through the aspirin-damaged mucosal barrier, which suggests inhibition of acid back diffusion as the mechanism of action. In vagotomized rats, the diffusion of H+ from the instilled acid solution into the gastric mucosa and outflux of Na+ from the mucosa into the lumen was so strong that aspirin could not show any acceleration of a back diffusion of H+ in contrast to the aspirin-free group. However, L-Glutamine given with or without aspirin inhibited the group. However, L-Glutamine given with or without aspirin inhibited the back diffusion of H+ instilled into the vagotomized rat stomach.

Influence of L-glutamine on aspirin-induced gastric lesions and absorptions as well as antipyretic, analgesic and anti-inflammatory effects of aspirin in rats and mice

L-glutamine markedly suppressed the development of the gastric lesions induced by aspirin in pylorus-ligated rats. In non-ligated normal rats, aspirin was absorbed rapidly after administration and was maintained in the blood in high salicylate concentration thereafter. When aspirin was administered in combination with L-glutamine, the absorption of aspirin was at nearly the same level as when aspirin had been given alone. In pylorus-ligated rats, administration of aspirin was followed by slow increment in blood salicylate concentration. Blood salicylate level in these rats was higher when aspirin was administered in combination with L-glutamine than when it had been given alone. Combined administration of aspirin and L-glutamine produced little influence on the antipyretic, analgesic and anti-inflammatory effects of aspirin in non-ligated normal rats.