Effect of nicotine, alcohol and caffeine pretreatment on the gastric mucosal damage induced by aspirin, phenylbutazone and reserpine in rats

The effects of nicotine (2.5 mg/100 ml), alcohol (25% v/v) and caffeine (30 mg/100 ml base) and their combination (nicotine, 2.5 mg/100 ml; alcohol, 25% v/v; and caffeine, 30 mg/100 ml base) fed in drinking water ad libitum for 21 days were studied on the gastric mucosal damage induced by aspirin, phenylbutazone and reserpine in rats. When given alone, none of them produced any visibly discernible gastric lesions. Their concurrent administration, however, produced some injury to the gastric mucosa which was far less severe than the lesions induced by any of the ulcerogenic drugs used in this study. Pretreatment with nicotine, alcohol and caffeine and their combination resulted in a significant augmentation of gastric lesions produced by aspirin, phenylbutazone and reserpine. These results establish an association between nicotine, alcohol and caffeine in the pathogenesis of gastric ulcers and also implicate them as modifying factors in the genesis of gastric lesions induced by aspirin, phenylbutazone and reserpine.     

Effect of a low-dose endotoxin pretreatment on the gastric mucosal damage induced by aspirin, phenylbutazone and reserpine in rats

The effect of endotoxin pretreatment (1 mg/kg body weight, i.p., once daily for 2 days) on the gastric mucosal damage induced by aspirin, phenylbutazone and reserpine has been studied in albino rats. When given alone, endotoxin did not produce any visibly discernible gastric lesions. It produced a significant augmentation of the gastric lesions produced by phenylbutazone and reserpine but did not significantly alter the ulcerogenicity of aspirin. The involvement of endogenous histamine formation and its release following phenylbutazone and reserpine administration and also in response to endotoxin pretreatment may be responsible for the exacerbation of gastric lesions induced by these drugs. Recent reports indicate the involvement of endorphins and platelet activating factor (PAF) in the ulcerogenic activity of endotoxin when used in high doses and their role in the potentiation of phenylbutazone- and reserpine-induced gastric lesions has to be worked out.     

Drugs and gastric damage.

The effects of aspirin, salicylate formulations and substitutes, smoking (nicotine), indomethacin, corticosteroids, phenylbutazone, ethanol, caffeine and reserpine on the gastric mucosa are discussed. The damaging effects of the drugs are considered in terms of the gastric mucosal barrier, gastric erosions, microbleeding and haematemesis and melaena and finally whether they cause peptic ulcer. There is suggestive evidence that unbuffered aspirin is a cause of haematemesis and melaena and of gastric ulcer but the incidence rates for hospital admission are low, being 10 to 15 per 100,000 heavy users per year. Aspirin in solution as acetylsalicylate buffered to maintain a neutral pH protects against gastric damage. Newer aspirin substitutes (mefenamic acid, fenoprofen, naproxen, tolmetin and ibuprofen) appear to cause less faecal blood loss than aspirin but their long-term effects have not been fully evaluated. Smoking is definitely associated with peptic ucler but the mechanism is unknown. Corticosteroids are probably not ulcerogenic despite clinical bias that they are. Indomethacin and phenylbutazone may be ulcerogenic but there is insufficient evidence to make firm judgements. Ethanol, caffeine and reserpine, on available evidence, are probably not ulcerogenic.     

Histidine decarboxylase inhibition: a novel approach towards the development of an effective and safe gastric anti-ulcer drug

The involvement of histamine in mediating gastric function under normal and pathological conditions has been largely established. The relationship between gastric acid production and peptic ulcer diathesis is also well known. Recently, endogenous histamine formation and its release from mast cells has been implicated in the pathogenesis of human and experimental gastric ulcers produced by restraint and pyloric ligation. It has also been implicated in the gastric mucosal damage produced by drugs like aspirin, phenylbutazone and reserpine. These observations suggest that histidine decarboxylase inhibitors may be useful in the prevention of such lesions. Our studies on the evaluation of some histidine decarboxylase inhibitors show that these compounds have a promising potential for developing an effective and safe anti-ulcer drug. This mini-review incorporates the results of our studies which have been adequately supported by other studies as well.     

Effects of fasting, stress and drugs on gastric glycoprotein synthesis in the rat.

1 The relationship between gastric mucosal damage and synthesis of gastric glycoproteins, as measured by the rate of incorporation of N-acetyl-[3H]glucosamine, was investigated in rats after fasting and restraint stress and a single administration of aspirin (200 mg/kg, orally), phenylbutazone (200 mg/kg, orally), prednisolone (200 mg/kg, orally), or adrenaline (2 mg/kg, i.p.). In one experiment, the effects of aspirin and phenylbutazone on carbohydrate content of the glycoproteins were also determined. 2 Restraint stress, phenylbutazone and aspirin resulted in acute gastric mucosal erosions in some of the rats. Adrenaline produced severe sub-mucosal haemorrhage, but no erosions or ulceration, while prednisolone and fasting gave no gross pathology. 3 The rate of incorporation of N-acetyl-[3H]glucosamine into glycoproteins was decreased after all treatments except adrenaline. In the groups receiving restraint stress, aspirin or phenylbutazone, the decreases were more marked in rats which developed erosions than in those with no gastric pathology. 4 Aspirin and phenylbutazone also produced changes in the carbohydrate content of the glycoproteins, the effects again being greater in the rats which developed erosions. 5 The results are discussed in the context of a possible association between erosion formation and glycoprotein synthesis and it is proposed that inhibition of mucus glycoprotein biosynthesis may be one mode of action of stress and drugs in causing gastric mucosal damage.     

Effect of caffeine on ibuprofen-induced gastric mucosal damage in rats.

During investigations on the effect of caffeine on ibuprofen-induced gastric mucosal lesions in rats, we have found that caffeine (p.o.) inhibits the development of ibuprofen-induced gastric lesions in a dose-dependent manner (ED50 18.4 mg kg(-1)). To investigate this protective effect of caffeine, we have studied the effect of caffeine on HCl-ethanol-induced gastric mucosal lesions with or without indomethacin pretreatment. Caffeine inhibited the development of HCl-ethanol-induced gastric lesions with and without indomethacin pretreatment. These results indicate that caffeine did not act as a mild irritant but, on the contrary, had protective effects. We measured the gastric mucosal prostaglandin E2 (PGE2) concentrations and gastric mucosal blood flow, as representative protective factors for gastric mucosa. Caffeine did not affect the gastric mucosal PGE2 concentrations 4h after administration of ibuprofen. However, topical administration of caffeine resulted in an increase in gastric mucosal blood flow, as measured by laser Doppler flowmetry. We investigated the gastric acid secretion and gastric mucosal myeloperoxidase activity as representative aggressive factors for gastric mucosa. When caffeine was administered intraduodenally in pylorus-ligated rats, gastric acid secretion decreased in a dose-dependent manner, with an ED50 of 44.9 mg kg(-1). Caffeine decreased ibuprofen-induced gastric myeloperoxidase activity in a dose-dependent manner, with an ED50 of 9.1 mg kg(-1). These findings indicate that caffeine, at least in rats, may inhibit the development of acute gastric mucosal injury. The mechanisms underlying the protective actions of caffeine are unclear, but may be related in part to an increase in gastric mucosal blood flow and suppression of neutrophil activation.     

Improvement of the gastric tolerance of non-steroidal anti-inflammatory drugs by polyene phosphatidylcholine (Phospholipon 100)

The effect of co-administration with polyene phosphatidylcholine (Phospholipon 100) on the oral gastrotoxicity of various non-steroidal anti-inflammatory drugs (NSAIDs) was studied in the rat. The highly unsaturated phospholipid reduced gastric mucosal lesions measured 3.5 h after oral administration of aspirin, indomethacin, phenylbutazone, diclofenac, piroxicam and sudoxicam to rats which had received a 3 day bread diet followed by 24 h fasting. The extent of reduction of gastrotoxicity varied amongst the individual NSAIDs. Phospholipon 100 also reduced gastric lesions induced by 3 day oral piroxicam and diclofenac administration. A trend towards reduction of oral diclofenac gastrotoxicity was observed following intravenous Phospholipon 100 administration. Phospholipon 100 H (100% saturated phosphatidylcholine) was less effective than Phospholipon 100 in improving acute gastric tolerance to oral phenylbutazone, diclofenac and piroxicam. Administration of the NSAID-Phospholipon 100 combination produced little change in the anti-inflammatory activities of diclofenac on carrageenan paw oedema and diclofenac and piroxicam on adjuvant arthritis in the rat. Combination with Phospholipon 100 offers a novel means for reducing the gastric side-effects of NSAID therapy.     

Gastroprotective effects of bitter principles isolated from Gentian root and Swertia herb on experimentally-induced gastric lesions in rats

Gentianae Radix, the dried root and rhizoma of Gentiana lutea L. (Gentianaceae), has long been used as a remedy for liver and stomach inflammation, eye troubles, etc. In this paper, the gastroprotective effects of the methanol extract of Gentian root (GM) were studied using different gastric lesion models. In pylorus-ligated rats, administration of GM in the duodenum suppressed gastric juice secretion and total acid output in a dose-dependent manner. Oral or duodenum administration of GM showed significant protection against acute gastric ulcer induced by aspirin plus pylorus ligation, water-immersion restraint stress-induced ulcers, and gastric mucosal injury induced by ethanol. Furthermore, four secoiridoid glycosides, amarogentin (A1), gentiopicroside (A2), amaroswerin (A3), and swertiamarin (A4), were obtained from Gentian root or Swertia herb, and their protective effects against stress-induced ulcers and ethanol-induced gastric mucosal injury were evaluated. The doses required for 50% inhibition (ID₅₀) of A1, A3, and A4 on stress-induced ulcers were calculated to be 5.76, 2.58, and 167 mg/kg respectively. The protective effect of A2 at 250 mg/kg was 26.5%. On ethanol-induced gastritis, 5.0 mg/kg of A1 and A3 showed remarkable suppressive effects (33.7 and 45.4%, respectively), and 20 mg/kg of A4 exhibited a suppressive effect (30.8%). The effects of A1, A3, and A4 on ethanol-induced gastric lesions were canceled by 5.0 mg/kg indomethacin pretreatment. These results suggest that the therapeutic effects of Gentian root on gastric lesions are associated with enhanced mucosal defensive factors via the prostaglandin pathway in the cell membrane, and that secoiridoid glycosides contribute to this activity.     

Gastric anti-ulcer and cytoprotective effect of selenium in rats

Selenium, a trace element, in the form of sodium selenite has been studied for its ability to protect the gastric mucosa against the injuries caused by hypothermic restraint stress, aspirin, indomethacin, reserpine, dimaprit, and various other gastric mucosal-damaging (necrotizing) agents in rats. The results demonstrate that oral administration of sodium selenite produces a significant inhibition of the gastric mucosal damage induced by all the procedures used in this study. Selenium, in a nonantisecretory dose, produced a marked cytoprotective effect against all the necrotizing agents. The cytoprotective effect of selenium against the effects of 80% ethanol and 0.6 M HCl was significantly reversed by prior treatment with a dose of indomethacin that inhibits prostaglandin biosynthesis. These data indicate that sodium selenite inhibits the formation of these lesions by the mucosal generation of prostaglandins. The concentrations of nonprotein sulfhydryls (NP-SH) were significantly decreased in the gastric mucosa following the administration of necrotizing agents--80% ethanol and 0.6 M HCl. Treatment with sodium selenite, which significantly reduced the intensity of gastric lesions, did not replenish the reduced levels of gastric mucosal NP-SH, thus ruling out the mediation of its protective effect through sulfhydryls. The antisecretory effect of sodium selenite, which becomes evident only in the high dose of 20 mumol/kg, may be responsible for the inhibition of gastric lesions induced by aspirin, indomethacin, reserpine, and dimaprit. Our findings show that selenium possesses significant anti-ulcer and adaptive cytoprotective effects. However, further detailed studies are required to confirm these effects, to establish its mechanism(s) of action, and to determine its role in the prophylaxis and treatment of peptic ulcer disease.     

A synergistic interaction between aspirin, or other non-steroidal anti-inflammatory drugs, and stress which produces severe gastric mucosal damage in rats and pigs.

A synergistic interaction was observed in the development of damage to the gastric mucosa of rats following the administration of a single oral dose of 50 or 200 mg/kg body weight aspirin and exposure to brief periods of cold or restraint stress. Under the experimental conditions employed, the stressed (control) animals did not develop any visible signs of damage while the rats given only aspirin developed typical small erosions. However, the animals given aspirin and simultaneously exposed to stress developed a large number of deep ulcers and massive haemorrhage. Similar results were obtained in rats given a variety of non-steroidal anti-inflammatory drugs, but not with dextropropoxyphene -- an analgesic devoid of ulcerogenic activity. In pigs, the chronic administration of aspirin and exposure to restraint stress resulted in the formation of deep crater-like ulcers. Only small focal lesions were found in the pigs given aspirin alone and no mucosal damage was evident in the pigs exposed only to stress. It appears that the aspirin plus stress synergism may be the basis for the formation of chronic gastric ulcers in humans.     

Effects of phenacetin,paracetamol and caffeine on the erosive activity of acetylsalicylic acid in the rat stomach: dose-response relationships,time course of erosion development and effects on acid secretion

Adult male and female Wistar rats were equally susceptible to gastric injury induced with acetylsalicylic acid (aspirin). Both in male and in female rats simultaneous administration of caffeine and aspirin caused significantly more gastric erosions than the same dose of aspirin alone; likewise addition of paracetamol to aspirin decreased the incidence of gastric lesions in either sex, and addition of phenacetin to aspirin had no effect. The potentiation by caffeine and the inhibition by paracetamol were both dose-dependent and only markedly influenced the development of erosions after 3–4 h. Pretreatment with phenacetin or paracetamol 1 h before administration of aspirin did not affect its erosive activity. Administration of benorylate caused no more gastric erosions than the vehicle or than equivalent mixtures of aspirin and paracetamol. The histamine-stimulated acid output of the stomach during gastric perfusion with aspirin was rapidly diminished. Neither paracetamol nor caffeine initially affected this decrease in acid output. However, 30 min after perfusion with aspirin and caffeine, acid secretion increased approximately as strongly as after caffeine alone. Caffeine potentiates aspirin-induced erosions by its stimulatory effect on acid secretion whereas paracetamol inhibits these erosions by preventing their growth.     

Studies on anti-ulcer effects of a new compound, zinc L-carnosine (Z-103)

We investigated the anti-ulcer effects of zinc L-carnosine (Z-103) using several acute experimental models of gastric and duodenal lesions in rats. Effects of Z-103 on various gastric functions, e.g., antacid (in vitro), anti-pepsin (in vitro), gastric secretion, mucosal potential difference (PD) and mucus contents were also examined. Z-103 given orally prevented development of gastric lesions induced by water immersion stress, histamine, HCl-aspirin, HCl-ethanol and also duodenal ulcers induced by mepirizole in a dose-dependent manner. In vitro, Z-103 had a greater antacid effect than sodium bicarbonate; and moreover, the potency of its anti-peptic action (IC50 = 8.7 mM) was higher than those of several other drugs (sodium bicarbonate, sucrose sulfate and aceglutamide aluminum). Intragastric treatment of Z-103 (100 mg/kg alone tended to increase PD, and it also significantly inhibited the decrease in PD induced by aspirin. In addition, pretreatment with Z-103 at 10 and 30 mg/kg (p.o.) significantly prevented the decrease in mucus contents in the gastric mucosa and also mucosal lesions by oral administration of ethanol. On the other hand, Z-103 was not so effective on both basal (pylorus-ligation preparation) and histamine-stimulated gastric secretion (Heidenhain pouch preparation). These results suggest that Z-103 is useful for the treatment of gastric and duodenal ulcers in humans.     

Gastric mucosal cytoprotection in the rat by cysteine

The free radical scavengers methyl-methionine sulphonium bromide and cysteine (5%) protected the rat gastric mucosa against ischaemic injury produced by reserpine (5 mg kg-1 i.p.). Pretreatment with 1 mL of 5% cysteine by gavage completely protected against injury rats with no ligation and 70% of rats with pyloric ligation after they had been given aspirin (200 mg kg-1 by gavage), a dose that produced gastric mucosal injury in 40% of rats with no ligation and 70% of rats with pyloric ligation after 4 h. Ethanol (1 mL of 40% solution by gavage) after 1 h produced gastric mucosal injury in all animals and pretreatment with 1 mL of 5% cysteine by gavage completely protected 80% of non-ligated and 70% of pyloric-ligated rats against this injury. This protection was not associated with any significant effect on H+ output. The data suggest that cysteine maintains gastric mucin by a mechanism independent of acid secretion.     

Effects of the new anti-ulcer agent KB-5492 on experimental gastric mucosal lesions and gastric mucosal defensive factors, as compared to those of teprenone and cimetidine.

Effects of KB-5492, a new anti-ulcer agent, on various experimental gastric mucosal lesions and mucosal defensive factors in rats were compared with those of teprenone and cimetidine. KB-5492 administered orally at 12.5-200 mg/kg inhibited water-immersion stress- and indomethacin-induced gastric mucosal lesions in a dose-dependent manner with ED50 values of 46 and 27 mg/kg, respectively, indicating that KB-5492 was more potent than teprenone but less potent than cimetidine. KB-5492, administered orally at 12.5-100 mg/kg, also inhibited ethanol-induced gastric mucosal lesions in a dose-dependent manner with an ED50 of 23 mg/kg, so KB-5492 was 3 times more potent than teprenone, whereas cimetidine produced no obvious inhibition. In addition, KB-5492, administered orally at 25 and 50 mg/kg twice daily for 10 consecutive days, significantly accelerated the healing of acetic acid-induced gastric ulcers more potently than teprenone and cimetidine. KB-5492 at anti-ulcer doses significantly increased gastric mucosal blood flow in normal anesthetized rats and inhibited the reduction of gastric mucosal hexosamine content induced by aspirin, but did not affect gastric acid secretion in pylorus-ligated rats. These results indicate that KB-5492 has potent and broad anti-ulcer properties, which are probably exerted by its enhancement of gastric mucosal defensive factors through increasing gastric mucosal blood flow and/or retaining gastric mucus, and not by its inhibition of gastric acid secretion.     

Effects of zinc acexamate on gastric mucosal resistance factors

The effects of zinc acexamate on gastric defensive systems were evaluated in the rat. Gastric ulcers induced by oral administration of three necrotic agents (0.6 N HCl, 25% NaCl, 100% ethanol) were markedly reduced by different pretreatments with zinc acexamate. This cytoprotective effect was not modified by previous treatment with indomethacin (30 mg/kg orally). Zinc acexamate pretreatment also prevents the disruption of the gastric mucosal barrier induced by aspirin (40 mM) and increases mucus production in the gastric glands and tracheal walls. These observations suggest that the antiulcer effects described for zinc salts could be the result, at least partly, of an action increasing gastric mucosal defensive systems.     

Ulcer formation and cytoprotection by acetazolamide

Acetazolamide, a carbonic anhydrase inhibitor, was administered orally and subcutaneously to rats. Acetazolamide increased the gastric ulcerogenicity of indomethacin, but inhibited gastric ulcers produced by acidified aspirin. When administered alone to fasted rats, it did not produce gastric ulcers. Acetazolamide was also cytoprotective for the stomach (it reduced dose dependently the number of gastric necrotic lesions caused by absolute ethanol given orally) and for the small intestine (it prevented dose dependently intestinal lesions produced by administration of a high dose of indomethacin). Acetazolamide did not prevent the antiulcer effect of PGE2 (against aspirin-induced ulcers) nor the cytoprotective effect of 16,16-dimethyl PGE2 (against ethanol-induced gastric lesions). The degree of gastric cytoprotection increased with time after a single administration of acetazolamide; the optimal effect occurred 60 and 90 min after oral and subcutaneous administration, respectively. Pretreatment with indomethacin completely prevented the cytoprotective effect of acetazolamide; this suggests that the cytoprotective effect may be mediated by endogenous release of prostaglandins by the stomach. All the effects of acetazolamide reported here were observed after either oral or subcutaneous administration. The mechanism by which acetazolamide influences ulcer formation and is cytoprotective is unknown.     

Gastric erosions induced by analgesic drug mixtures in the rat.

Gastric erosions after oral administration of analgesics separately and in admixture have been examined in adult rats. After administration of acetylsalicylic acid (aspirin), phenacetin, paracetamol and caffeine as single drugs, gastric erosions were only observed with aspirin. The combination of aspirin with phenacetin did not change, that of aspirin with caffeine significantly increased, and aspirin with paracetamol significantly decreased the incidence of gastric lesions compared with aspirin alone. The results for aspirin with paracetamol did not differ from those for the vehicle. Addition of caffeine to the combination of aspirin and phenacetin caused a significant increase in erosions, but when given with aspirin and paracetamol no erosions occurred. The mechanisms underlying the effects of these drugs on aspirin-induced erosions are discussed.     

Gastric erosions induced by analgesic drug mixtures in the rat

Gastric erosions after oral administration of analgesics separately and in admixture have been examined in adult rats. After administration of acetylsalicylic acid (aspirin), phenacetin, paracetamol and caffeine as single drugs, gastric erosions were only observed with aspirin. The combination of aspirin with phenacetin did not change, that of aspirin with caffeine significantly increased, and aspirin with paracetamol significantly decreased the incidence of gastric lesions compared with aspirin alone. The results for aspirin with paracetamol did not differ from those for the vehicle. Addition of caffeine to the combination of aspirin and phenacetin caused a significant increase in erosions, but when given with aspirin and paracetamol no erosions occurred. The mechanisms underlying the effects of these drugs on aspirin-induced erosions are discussed.     

The effect of ethanol-caffeine interaction on the gastric mucosal barrier

Potential difference across the stomach wall (PD) is determined by the gastric mucosa electrolyte barrier. The decrease in the PD caused by the "barrier breakers" e.g. aspirin, alcohol and cholic acids is a sensitive index of mucosal damage. We studied the effect of interaction between alcohol and caffeine on the PD in the anesthetized rats. The intragastric administration of 1 ml of 40 vol.% ethanol solution decreased the PD by 39%, of 10 mg of caffeine sodium benzoate by 22% and the simultaneous administration of alcohol and caffeine by 53%. These results indicate that caffeine may enhance the damaging effect of alcohol on the gastric mucosal barrier.     

Gastric mucosal lesions in rats induced by the communication box paradigm: experimental conditions, endoscopic observation, and effect of vagotomy

A communication box paradigm which can eliminate the influence of the physical noxious stimuli such as electrical foot-shock from the conditioned emotional stimuli has recently been developed for producing gastric mucosal lesions (GML) in mice. In this situation, the unshocked animals (NE group) were exposed to affective stimuli such as visual, auditory and olfactory sensations from the shocked conspecifics (E group). The present study was conducted to investigate an experimental procedure that can be applied to rats. When the communication box paradigm was applied to rats, the incidence of GML was very low: E group (38%) and NE group (13%). Marked augmentation of the incidence of GML was obtained in both E and NE groups by reserpine pretreatment at the dose of 1 mg/kg which did not produce GML. Various kinds of GML were defined endoscopically using a narrow fibre scope. The manifestation of the GML in both E and NE groups was completely suppressed by vagotomy, whereas pyloroplasty was ineffective. The procedure for eliciting GML in rats was established by a combination of the communication box paradigm with reserpine pretreatment. The endoscopic technique may provide a clue for investigating the time-dependent healing process of GML, especially for evaluating the therapeutic effect of a drug.