The effects of drugs on the production and recovery processes of the stress ulcer

Studies of the mechanisms of gastric bleeding under obstructive jaundice. Role of biogenic amines

Mechanisms of gastric bleeding under obstructive jaundice were studied in adult male Wistar rats. Following ligation of the common bile duct, mucosal noradrenaline significantly decreased in both the pyloric and fundic gland areas of the gastric mucosa by 20 days after the operation. Serotonin increased only in the pyloric gland area, and histamine increased in the fundic gland area. Urinary excretion of free noradrenaline significantly increased after the ligation. Three weeks after the ligation, restraint and water immersion experiments were conducted. Under water immersion, gastric blood flow significantly reduced in rats with obstructive jaundice compared to controls. Acid output decreased in both groups. Gastric bleeding was noted in the fundic gland area significantly earlier in the ligated rats than in the non-ligated rats. Administration of noradrenaline s.c. 30 minutes before immersion significantly blocked the reduction in gastric blood flow and protected the gastric mucosa against acute bleeding under immersion. These results suggested that prolonged obstructive jaundice may deplete noradrenaline in the gastric mucosa, and that gastric mucosal ischemia caused by this sympathetic dysfunction plays an important role in the formation of acute gastric bleeding under obstructive jaundice.

Neural regulation of adrenal chromaffin cell function in the mouse--stress effect on the distribution of [3H]dopamine in denervated adrenal medulla

Effects of adrenal denervation and stress on the distribution of radioactivity in the adrenal medulla after [3H]dopamine injection was studied by light microscopic autoradiography. Denervation of the adrenal gland abolished the stress (restraint plus water immersion) induced degranulation of adrenal chromaffin cells and decreased uptake of [3H]dopamine. Denervated chromaffin cell of stress mice incorporated as high radioactivity as those of no stress mice. Adrenal denervation increased the uptake in adrenaline-storing (A) cells but not in noradrenaline-storing (NA) cells. The characteristic distribution of radioactivity (high radioactivity along the cortico-medullary junction) was reinforced by adrenal denervation. Under stress conditions, increase in pituitary adrenocortical system did not enhance the uptake of [3H]dopamine in chromaffin cell while increase in nerve activity suppressed the uptake. Spontaneous activity of the splanchnic nerve to adrenal chromaffin cells suppresses the uptake of [3H]dopamine. The neural influence is stronger on A cells than on NA cells. Chromaffin cells in the subcortical zone are more intensely controlled by the neural influence than those in the central zone.

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.

The increase in putrescine content in the gastric mucosa of rats with ulcerations induced by restraint-immersion stress

By means of high-performance liquid-chromatography, the putrescine, spermidine and histamine contents in the gastric mucosa were examined during the course of ulceration in rats by the restraint-immersion stress. (1) The putrescine content increased progressively during the course of ulceration with the continuing stress whereas after being released from the stress the content decreased gradually to a significantly lower level than that immediately after 12 hours of the stress. (2) The spermidine content in the gastric mucosa was unchanged during the course of ulceration with continuing stress nor after being released from the stress. (3) The mucosal histamine content decreased significantly after 4 hours under the continuing stress. (3) Extensive histological examination revealed the appearance of regenerating epithelium 36 hours after being released from the stress whereas no such finding was seen before that period. From the above findings, it has been speculated that the increase in the gastric mucosal putrescine content during the course of ulceration induced by restraint-immersion stress is probably due to the stimulated adrenal function by the stress, independently of the regeneration of gastric mucosa.

Effects of cimetidine, atropine and prostaglandin E2 on rat mucosal erosions produced by intragastric distension

The effects of three typical antisecretory agents: cimetidine, atropine and prostaglandin E2 were compared on an acute rat gastric ulcer model which consisted of perfusing the stomach continuously, at a high intraluminal pressure (120 mm H2O), with a simulated gastric juice (0.1 M HCl plus 600 mg pepsin/l). As the acid and pepsin are given exogenously the inhibitory action of the antisecretory drugs is obviated in this model. Cimetidine and atropine failed to reduce gastric erosions, whereas prostaglandin E2 markedly reduced the severity of the mucosal lesions with respect to control values. Long-term treatment with cimetidine also failed to increase the resistance of the gastric mucosa to the digestive action of the artificial gastric juice. These findings indicate that only prostaglandin E2 is cytoprotective and do not support the view that anticholinergics or histamine H2-receptor antagonists have a cytoprotective role on the cells of the gastric mucosa.

Effects of water-immersion stress on gastric secretion and mucosal blood flow in rats

The correlation between acid secretion and mucosal blood flow in the rat stomach during stress loading was determined to provide clues to the etiology of the gastric ulceration which thus occurs. The gastric acid output was increased remarkably by water-immersion stress at 23 degrees C, and this increase lasted while the stress was given, yet the mucosal blood flow did not show a corresponding increase. In rats stressed for 3 hr, ulcerative changes were observed in the glandular portion of the stomach. The stress-induced increase in acid output correlated well with the severity of erosions. Pretreatment of animals with atropine 10 microgram/kg, given subcutaneously, or vagotomy, inhibited the increase in acid output and also inhibited the ulcer formation caused by the stress: however, the mucosal blood flow in these animals decreased significantly. These results suggest that when there is an elevation of gastric acid secretion with no parallel increase in mucosal blood flow, gastric ulceration may occur under conditions of stress.

Role of gastric motility in development of stress-induced gastric lesions of rats

Gastric motility of stressed rats was studied to determine its role in producing stress-induced gastric lesions. Restraint and water immersion resulted in an increase in gastric motility which consisted of an increase in frequency and amplitude of contractions and a rise in gastric tone. This increase reached maximal levels 2 to 4 hr after stress, and persisted thereafter. Formation of gastric lesions was markedly accelerated after occurrence of the increased gastric motility. In contrast, restraint alone neither produced such a vigorous increase in gastric motility, nor were the gastric lesions severe. A continuous infusion of papaverine during restraint and water immersion inhibited increase in frequency and amplitude of gastric contractions and prevented formation of gastric lesions. It is concluded that increased gastric motility is closely associated with marked formation of gastric lesions under conditions of restraint and water immersion stress and is probably a main cause for their vigorous formation, although formation of lesions occurs to a small degree without involvement of gastric motility.

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.

Influences of ulcerogenic stimulations in the stomach with the clamping ulcers in rats

Ulcerogenic stimulations such as histamine and restraint water immersion stress were given to rats after the gastric ulcers were made by the clamping method. Development of the stress and histamine ulcers were distinctly inhibited after the clamping ulcers were made, and this inhibition reached a maximum at the 7th clamping ulcer day and lowered gradually thereafter. In control rats, the stress and histamine ulcers usually develop in the lesser curvature, but in animals with the clamping ulcers they develop in the greater curvature where the clamping ulcer was made. The histological changes of the stress ulcers in the stomach with the clamping ulcer were slighter compared with those of the control (without clamping ulcers) rats. Furthermore, the relationships between the development of the stress ulcers and the changes of the uronic acid content in the stomach were observed. The uronic acid content increased after the clamping ulcer was made and reached a maximum at the 7th clamping ulcer day. Thereafter it began to decrease and returned to the normal level. From the results of the studies, it was strongly suggested that the mechanism of inhibition to development of the stress ulcers might be attributed to an increase of acid mucopolysaccharide in the gastric wall after the clamping ulcer was induced.

The effects of destruction of noradrenergic ascending ventral bundles and tetrabenazine on formation of stress-induced gastric ulcer

The possibility that hypothalamic noradrenaline (NA) plays a role in the formation of gastric ulcers under stress via ventral bundles (VB) was examined in rats after bilateral destruction of VB. After a 3-h restraint stress ulcerative changes were observed in the stomach of sham-operated rats. NA contents in the hypothalamus and cerebral cortex decreased as compared to the respective contents before stress. The VB-lesioning inhibited the stress-induced decrease of NA in the hypothalamus. Ulcer indices in the animals 1 or 7 days after the VB-lesioning, however, did not differ from those of controls. Pretreatment of sham-operated controls with tetrabenazine enhanced the stress-induced decrease of NA in the brain, and exacerbated the gastric ulceration. VB-lesioning completely blocked these effects of tetrabenazine. It appears that the tetrabenazine-induced mobilization of hypothalamic NA via VB causes an aggravation of gastric ulceration.

A new model of stress ulcer in the rat with pylorus ligation and its pathogenesis

Water-immersion stress for 7, 14, or 20 hr consistently induced linear or punctate stress ulcers (mucosal erosions) in the corpus of the stomach in intact rats. When the pylorus of the stomach had been ligated prior to stressing, the stress ulcers changed their morphological feature (mainly punctate and in one place elongated) and location (both in corpus and antrum). Histologically, the stress ulcer developed in the proximal antrum of pylorus ligated rats and penetrated into the muscularis mucosa. Sodium bicarbonate, chlorpromazine, hexamethonium, atropine, metiamide, and bilateral vagotomy markedly inhibited the stress ulcers which developed in the pylorus-ligated rats. Phentolamine and propranolol hardly affected the development of stress ulcers. Amylopectine evoked a new type of stress ulcer in the corpus when it was given to the pylorus-ligated rats.

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.

Effects of stress and of autonomic blockers on gastric mucosal microcirculation in rats

Changes in gastric mucosal microcirculation in rats were studied by using the method of intra-aortic injection of India ink, followed by microdissection of the mucosa. Acute stress, induced by restraint and exposure to cold for 2 hr, caused marked and significant vasodilatation in the gastric mucosa. This vasodilatation was prevented by pretreatment with atropine or chlorpromazine, but not by alpha- or theta-adrenoceptor blocking agents. Phentolamine caused significant vasoconstriction in the gastric mucosa of non-stressed rats, but when animals were stressed phentolamine induced a greater vasodilatation than was obtained with stress alone. These observations provide added support for the hypothesis that stress induces vagal overactivity, probably of central origin. The resulting strong contractions of the gastric wall, and compression of the intramural vessels, are probably responsible for degeneration of the mucosal cells leading to the formation of stress-induced ulcers in the rat.

Inhibitory effect of L-glutamine on the aspirin-induced gastric lesions in the rat

The effects of an amino acid, L-glutamine, on aspirin-induced gastric lesions and gastric secretion were studied in either intact or pylorus-ligated rats. L-Glutamine had a pronounced inhibitory effect on gastric lesions induced by aspirin administered by oral, intraperitoneal, or intraduodenal routes to intact or pylorus-ligated rats. By the oral route the inhibition was dose-related. However, L-glutamine given either intraduodenally or intraperitoneally did not show any appreciable effects on gastric lesions induced by orally administered aspirin in pylorus-ligated rats. One mechanism of L-glutamine protection was inhibition of a back diffusion of gastric acid caused by aspirin and this was demonstrated in pylorus-ligated rats. The reduction in H+ and increase in Na+ concentrations in the lumen caused by aspirin was returned to normal by increasing doses of L-glutamine. In addition, L-glutamine was considered to inhibit the back diffusion of acid caused by pylorus ligation per se, because the amino-acid produced an increment of H+ and reduction of Na+ and K+ in comparison with the control group. The role of pepsin on L-glutamine protection was negligible.