Studies on the role of acid in the pathogenesis of experimental stress ulcers

Protective Effect of Ginger oil on Aspirin and Pylorus Ligation-Induced Gastric Ulcer model in Rats

The present investigation was performed in aspirin and pylorus ligation-induced ulcer model in Wistar rats, in which ability of ginger oil to provide gastric protection was studied at two different doses, 0.5 and 1 g/kg po. Gastric protection was evaluated by measuring the ulcer index, serum γ-GTP levels, total acidity of gastric juice and gastric wall mucus thickness. The results obtained in the present study indicated that ginger oil has a protective action against gastric ulcers induced by aspirin plus pylorus ligation in Wistar rats.

Comparison of tolerance and change of intragastric pH between early nasogastric and nasojejunal feeding following resection of colorectal cancer

BACKGROUND

Early feeding after injury has been suggested to decrease morbidity and mortality in many studies. Intrajejunal feeding has been preferred over intragastric feeding due to earlier return of peristalsis following laparotomy. Few reports, however, have focused on the tolerance and change in pH inside the stomach after intragastric and intrajejunal feeding. The aim of the present study was the assessment of (1) the postoperative tolerance of intragastric and intrajejunal feeding, and (2) the effect of intragastric and intrajejunal feeding on intragastric pH value.

MATERIALS AND METHODS

From April 1998 to October 2002, 140 patients underwent colon resection for colorectal cancer entered the study. The patients were divided into seven groups of 20 patients each. Group I was kept on NPO for 1 week. Groups II, III, and IV were fed through a nasogastric (NG) tube from the second to the sixth postoperative day (POD) with low residual (Osmolite-HN), high-fat (Pulmocare), and glutamine-containing (AlitraQ) enteral formulas, respectively. Groups V, VI, and VII were fed through a nasojejunal (NJ) tube from the second to the sixth POD with Osmolite-HN, Pulmocare, and AlitraQ, respectively. Feeding started at 500 kcal/500 cm(3)/d. If the patient tolerated the formula well, feeding increased to 1,500 kcal/1,500 cm(3)/d the following day. Intragastric pH was measured preoperatively and then twice daily until the sixth POD.

RESULTS

Poor tolerance occurred in 14 patients (23%) with NG tube feeding and 18 patients (30%) with NJ tube feeding. The pH value of intragastric juice increased significantly once NG feeding started (3.67+/-1.33 on the third POD; 4.28+/-1.26 on the sixth POD). However, the pH value remained low after NJ feeding was started (2.09+/-1.46 on the third POD; 2.14+/-1.49 on the sixth POD).

CONCLUSIONS

This series suggests that (1) the majority of patients can tolerate early feeding well following resection of colorectal cancer, and NJ feeding is not necessarily better tolerated than NG feeding; (2) early NG, but not the NJ feeding, can significantly elevate the intragastric pH value in patients who underwent resection of colorectal cancer. NG may be more effective than NJ feeding in preventing stress-induced gastropathy by elevating the pH value of intragastric juice.

Evidence for frequency-dependent arterial damage in vibrated rat tails

The effects of single 4-hr bouts of continuous 30, 60, 120, and 800 Hz tail vibration (49 m/sec2, root mean squared) were compared to assess frequency-amplitude-related structural damage of the ventral caudal artery. Amplitudes were 3.9, 0.98, 0.24, and 0.0055 mm, respectively. Vibrated, sham-vibrated, and normal arteries were processed for light and electron microscopy. The Curry rat tail model of hand-arm vibration (Curry et al. Muscle Nerve 2002;25:527-534) proved well-suited for testing multiple frequencies. NFATc3 immunostaining, an early marker of cell damage, increased in smooth muscle and endothelial cells after 30, 60, and 120 Hz but not 800 Hz. Increased vacuolization, which is indicative of smooth muscle contraction, occurred for all frequencies except 800 Hz. Vacuoles increased in both endothelial and smooth muscle cells after 60 and 120 Hz. Only 30 Hz showed pronounced smooth muscle cell vacuolization along the internal and external elastic membranes, suggesting stretch-mediated contraction from the large amplitude shear stress. Discontinuities in toluidine blue staining of the internal elastic membrane (IEM) increased for all frequencies, indicating vibration-induced structural weakening of this structure. Patches of missing IEM and overlying endothelium occurred in approximately 5% of arteries after 60, 120, and 800 Hz. The pattern of damage after 800 Hz suggests that the IEM is disrupted because it resonates at this frequency. Vibration acceleration stress and smooth muscle contraction appear to be the major contributors to arterial damage. The pattern of vibration-induced arterial damage of smooth muscle and endothelial cells is frequency-amplitude-dependent.

Omeprazole is more effective than a histamine H2-receptor blocker for maintaining a persistent elevation of gastric pH after colon resection for cancer

BACKGROUND

An assessment was made of the change and the effect of a histamine H(2)-receptor blocker (H(2)-blocker) or omeprazole on gastric pH after surgery.

METHODS

Eighty patients who underwent colon resection for colorectal cancer were divided into groups of 20. Group I received neither H(2)-blocker nor omeprazole. Group II received cimetidine hydrochloride 1,200 mg daily, group III received ranitidine hydrochloride 200 mg daily, group IV received omeprazole 40 mg twice daily for 5 days. Gastric juice was measured preoperatively and then twice daily until the fifth postoperative day.

RESULTS

The gastric pH decreased after surgery. The gastric pH increased on the first postoperative day after the administration of H(2)-blockers (P <0.001), but started to decrease on the second postoperative day. The gastric pH increased and remained high throughout the study period for the omeprazole group (P <0.001).

CONCLUSIONS

The administration of an H(2)-blocker can significantly elevate the gastric pH value for patients after resection of colorectal cancer, but only lasts for 24 to 48 hours. Omeprazole is more effective than an H(2)-blocker at maintaining a persistent elevation of gastric pH.

Assessment of intragastric pH value changes after early nasogastric feeding

Studies have suggested that early feeding after injury decreases morbidity and mortality. Few reports, however, have focused on the change in pH inside the stomach after early tube feeding. The aim of the present study was the assessment of 1) the change in intragastric pH after surgery, and 2) the effect of early nasogastric tube feeding on intragastric pH value. From April 1997 to February 1998, 80 patients who underwent colon resection for colorectal cancer by a single surgeon entered the study and were randomized into four groups. Twenty patients (group I) were kept on NPO for 1 wk, and 20 patients per group (groups II, III, and IV) were fed through a nasogastric tube from the second to the seventh postoperative day with low-residual (Osmolite HN), high-fat (Pulmocare), and glutamine-containing (AlitraQ) enteral formulas. Feeding started at 500 kcal/500 cc/d. If the patient tolerated the formula well, feeding increased to 1500 kcal/1500 cc(-1)/d(-1) the following day. Intragastric pH was measured preoperatively and then twice daily until the sixth postoperative day. The pH value of intragastric juice increased significantly once feeding started (3. 67 +/- 1.33 on the third postoperative day; 4.28 +/- 1.26 on the six postoperative day). The pH value seemed only mildly affected by the patient's tolerance for tube feeding (poorly tolerated group, pH 3. 52 +/- 1.75 versus 3.75 +/- 1.21 in the well-tolerated group on the third postoperative day; poorly tolerated group, pH 3.67 +/- 1.02 versus 4.45 +/- 1.27 in the well-tolerated group on the sixth postoperative day). The pH value of intragastric juice was higher in group II than in groups III and IV (4.51 +/- 1.57, 3.90 +/- 1.20, 4. 42 +/- 0.89 respectively, on the sixth postoperative day). This series suggests that early nasogastric feeding can significantly elevate the intragastric pH value in patients after resection of colorectal cancer. Nasogastric feeding may decrease the incidence of stress ulceration by elevating the pH value of intragastric juice.

Use of animal models in peptic ulcer disease

Considerable progress has been made in the understanding of the formation of gastric erosions by the use of animals. The role of gastric acid secretion in their pathogenesis has been clarified. Gastric erosions are associated with the presence of acid in the stomach and slow gastric contractions. With several different experimental procedures, the animal's body temperature falls; preventing the fall averts erosions. A fall in body temperature or exposure to cold are associated with the secretion of thyrotropin-releasing hormone (TRH), and both increased and decreased concentration of corticotropin-releasing factor (CRH) in discrete regions of rat brains. Thyrotropin-releasing hormone when injected into specific sites in the brain produces gastric erosions and increases acid secretion and slow contractions, whereas CRH has the opposite effects. One of the major sites of interaction of the two peptides is in the dorsal motor complex of the vagus nerve. Thyrotropin-releasing hormone increases serotonin (5-HT) secretion into the stomach. Serotonin counter-regulates acid secretion and slow contractions. Many other peptides injected into discrete brain sites stimulate or inhibit gastric acid secretion.

Effects of KW-5805, a new antiulcer agent, on experimental gastric and duodenal ulcers, gastric mucosal lesions by necrotizing agents and gastric acid secretion

Effects of KW-5805, a new antiulcer agent, on various experimental ulcers, necrotizing agent-induced gastric lesions and gastric acid secretion in rats were compared with those of pirenzepine and cimetidine. KW-5805 showed antiulcer activities against experimental gastric and duodenal ulcers (ED50 = 1.2-10.0 mg/kg, p.o.). KW-5805 effectively inhibited gastric lesions induced by various necrotizing agents (ED50 = 4.5-39.8 mg/kg, p.o.). In addition, the cytoprotective effect of KW-5805 was not affected by indomethacin, but reserved by N-ethylmaleimide. These antiulcer and cytoprotective effects of KW-5805 were more potent than those of pirenzepine and cimetidine. In pylorus-ligated rats, intraduodenal KW-5805 administration at 30 mg/kg showed a weak antisecretory effect, which was 3-10 times less potent than those of pirenzepine and cimetidine. In rats with acute gastric fistula, intravenous injection of KW-5805 reduced methacholine-stimulated gastric acid secretion at doses of 10 and 30 mg/kg and inhibited tetragastrin-induced acid secretion at 30 mg/kg. These results indicate that KW-5805 has potent and broad antiulcer properties, which are probably exerted by its potent cytoprotective effect in addition to its antisecretory effect.

Effect of parathyroid hormone, centrally or peripherally injected, on gastric activity in male rats

Parathyroid hormone (PTH) injected peripherally did not interfere with the development of experimental ulcers. Conversely, when PTH was administered i.c.v. the development of ulcers was significantly inhibited. The gastric secretory volume and acid output were also reduced. The possibility is discussed that this antisecretory activity of PTH may be due to a direct effect at the CNS level.

Restraint stress in biomedical research: a review

The use of restraint or immobilization for investigations of animal physiology, pathology and pharmacology has an extensive history. The major use of this technique has been as a "stressor" for the induction of stress response syndromes in animals. Many such syndromes have been characterized from the behavioral level to the neurochemical concomitants of stress. As a consequence of this particular use of the restraint procedure, much information concerning drug effects on stress response syndromes has been obtained. Indeed, many researchers in the area of gastrointestinal drugs routinely screen their new compounds in a restraint model of gastric stress ulcer. The purpose of this review is to present for researchers, a summary of the methods for, the parameters of, and known drug effects on, restraint-induced pathology. In our experience, this technique has proven to be a very useful one for the examination of both central and peripheral mechanisms of stress-related disorders, as well as for studying drug effects upon these disorders.

Inhibition of restraint stress by systemic (Asu1,7) eel-calcitonin

The effects of different doses of (Asu1,7) eel-calcitonin, iv injected, on gastric secretion were studied in conscious rats with pyloric occlusion. Moreover, we evaluated the activity of this analogue on gastric ulcer formation by restraint stress. It was found that 2.5 or 5 Ul/kg (Asu1,7) eel-calcitonin decreased gastric acid secretion and inhibited the development of stress-induced ulcers in rats. In the isolated rat stomach the peptide at the concentrations of 1 nM to 1 microM did not modify acetylcholine, histamine or 5-hydroxytriptamine-induced contractions. These results suggest that this peripheral activity of (Asu1,7) eel-calcitonin does not involve a direct interference with cholinergic, histaminergic or serotonergic pathways at gastric level.

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.

The gastric antisecretory activity of 3-methoxy-5,7,3'4'-tetrahydroxyflavan (ME)--a specific histidine decarboxylase inhibitor in rats

3-Methoxy-5,7,3'4'-tetrahydroxyflavan (ME), a specific histidine decarboxylase inhibitor, has been shown to significantly reduce the gastric acid secretion and gastric tissue histamine levels in 6 h pylorus ligated rats. It has been found to be as effective as cimetidine in reducing the gastric acid secretion. However, cimetidine does not affect the gastric tissues histamine levels in the normal or pylorus ligated rats. These observations clearly establish that the two drugs reduce the gastric acid secretion by different mechanisms and suggest that their combination may show a potentiated gastric anti-ulcer activity.

The role of glucose in preventing stress gastric mucosal injury

Reports from other investigators have shown the ability of pretreatment with either parenteral (glucose) or enteral (bolus Vivonex HN) nutrition to protect against stress ulcer formation, suggesting that the mechanism of protection may be substrate availability. However, these prior animal studies have used inordinately high amounts of Vivonex HN (equal to 1050 ml/hr in a human). This study compared cytoprotection afforded by pretreatment with a continuous infusion of Vivonex HN at a more clinically applicable level to that of both parenteral (ip) and enteral (po) glucose to test the above hypothesis. One hundred eight rats were infused (0.1 ml/min) for 30 min with: po water, ip water, po 25% glucose, ip 25% glucose, or po Vivonex HN. This was followed by 2 hr of cold-restraint stress. Serum glucose was determined. Poststress, animals were sacrificed, stomachs inspected, and mean ulcer index was calculated. Only oral 25% glucose offered significant gastric cytoprotection. Serum glucose was highest in both glucose groups.

CONCLUSIONS

(1) Vivonex HN pretreatment failed to cytoprotect in this model, (2) gastric cytoprotection by oral but not by parenteral glucose in the presence of similar serum glucose levels suggests that luminal factors, in addition to substrate availability, are necessary for this protection to occur.

Central and peripheral sites of action for the protective effect of opioids of the rat stomach

Rats exposed to combined cold and restraint exhibited a reduced intensity of gastric damage when pre-treated intraperitoneally with morphine HCl or with the synthetic enkephalin analog [D-Ala2, MePhe4, Met(0)5ol]enkephalin (FK 33-824). Morphine HCl and FK 33-824 prevented some of the indices of the lesion also when injected intracerebroventricularly; morphine methyliodide, quaternary derivative of morphine with does not cross the blood brain barrier, was fully effective, by intraperitoneal route, in preventing the gastric damage. Both peripheral and central mechanisms seem, therefore, involved in the protective effect of opioids on rat gastric mucosa. Morphine HCl and FK 33-824 reduced significantly gastric acid secretion when administered intracerebroventricularly or intraperitoneally; in addition, a concomitant increase of prostaglandin production was observed in rat gastric mucosa after i.p. administration of both opioids. Both these events might contribute to the protective action of opioids on the stomach.

Intraventricular calcitonin inhibits gastric acid secretion

Parenteral and intracerebroventricular administration of calcitonin in rats resulted in the suppression of gastric acid secretion. This suppression also occurred in rats with insulin-induced hypoglycemia and after the administration of thyrotropin-releasing hormone. Intracerebroventricularly administered calcitonin was 1000 times more effective than parenterally administered calcitonin in suppressing gastric acid secretion. Calcitonin also inhibited the development of stress-induced ulcers in rats.

Gastric emptying and secretion in monkeys during unavoidable shock

Gastric fluid and acid secretory rates as well as concurrent fractional emptying rates were determined in monkeys subjected to repeated sessions of unavoidable shock. None of these variables changed from control levels during the first session but, by the last session, acid output was significantly reduced.

Prevention of acute gastric ulceration in the rat by cimetidine, a histamine H2-receptor antagonist

1. Intraperitoneal injections of cimetidine into rats markedly reduced gastric acid production. When given at a dose of 50 mg/kg body weight, rate of acid production fell from a mean of 2.73 mumol/min (s.d. = 0.32) to a lowest level of 0.81 (s.d. = 0.28): the difference was highly significant (P less than 0.005). When given in a dose of 100 mg/kg, the rate of acid production further fell to 0.18 mumol/min (s.d. = 0.12;P less than 0.001). 2. Treatment with cimetidine in doses of 100 mg/kg 8-hourly during a 24 h period of restraint prevented the development of acute gastric ulceration in the rat. Pretreatment with cimetidine also protected against the ulcerogenic effects of intragastrically administered bile or lysolecithin. 3. The marked sustained reduction of acid production most probably accounts for the protective effects of cimetidine against ulcer production in the rat stomach.

Vendor differences in starvation-induced gastric ulceration

The incidence of starvation-induced gastric lesions was observed in Sprague-Dawley rats obtained from four different vendors (ARS/Sprague-Dawley, Hilltop, Holtzman, and Charles River). Food was withheld for 5 days from rats weighing 150, 200, 260 or 330 g. Glandular lesions occurred in 150 g rats; rumenal lesions occurred in 200+ rats. ARS/Sprague-Dawley rats developed more glandular lesions, whereas Hilltop rats developed more rumenal lesions.