Gastric mucosal blood flow in rats after administration of 16,16-dimethyl prostaglandin E2 at a cytoprotective dose

The purpose of the present study was to determine whether the gastric cytoprotective effect of a prostaglandin such as 16,16-dimethyl prostaglandin (dmPGE2) is mediated by an increase in mucosal blood flow. Gastric mucosal blood flow was measured in urethane-anesthetized rats by the hydrogen gas clearance technique. In control rats given no ethanol, intragastric administration of dmPGE2 (10 micrograms/kg body wt) produced a significant reduction (15.3%) in gastric mucosal blood flow 30 min after treatment. This dose of dmPGE2 significantly reduced the formation of the gross gastric lesions produced by absolute ethanol in anesthetized rats. In vehicle-pretreated animals, blood flow was invariably absent in the ethanol-induced mucosal lesion areas. In the nonlesion areas, gastric mucosal blood flow was the same in prostaglandin-pretreated and vehicle-pretreated animals as in control (no ethanol) rats. Thus, although dmPGE2 pretreatment protected against ethanol-induced gastric mucosal injury and prevented the accompanying blood flow stasis, it did not do this by an increase in gastric mucosal blood flow. The protection also is not due to a decrease in flow because, in separate groups of anesthetized rats, a 15% reduction in gastric mucosal blood flow induced by either hemorrhage or intravenous vasopressin did not protect the gastric mucosa against absolute ethanol-induced injury. Whether the maintenance of gastric mucosal blood flow is a primary or secondary effect of prostaglandin cytoprotection remains to be determined.     

Protective Effect of a Vasopressin-1 Selective Antagonist, OPC-21268, Against Ethanol-Induced Damage of The rat Gastric Wall

Since endogenous vasopressin has been reportedto be an aggressor in the gastric mucosa and avasoconstrictor in the gastric circulation, weinvestigated the gastric cytoprotective effects ofOPC-21268, a newly developed, nonpeptide, orally activevasopressin-1 receptor antagonist, on ethanol-inducedgastric injury in rats. The rats were treated withOPC-21268 or placebo 2 hr before ethanol administration, and the gastric mucosa was evaluatedmacroscopically for ulcer damage, and histologically forgastric mucosal injury. Gastric mucosal blood flow,erythrocyte volume, and erythrocyte velocity were alsomeasured in groups given saline, ethanol alone, andethanol after OPC-21268. To investigate the role ofsystemic or locally secreted vasopressin, we measuredplasma and tissue (gastric mucosa) vasopressinconcentrations after ethanol or vehicle administration.Prophylactic OPC-21268 treatment improved the gastriculcer score in a dose-dependent manner, and histologicalexamination demonstrated that the drug significantly ameliorated the gastric injury induced byethanol. The hemodynamic values obtained in theOPC-21268-treated and ethanol-treated group were similarto those in the saline control group, but values weresignificantly (P < 0.05) higher for gastric mucosal bloodflow and erythrocyte velocity and lower for erythrocytevolume compared to the group given ethanol alone. Plasmavasopressin concentrations were not significantly different in the control group and at 15, 30,and 60 min after administration of ethanol. However,ethanol administration caused a threefold increase ingastric tissue vasopressin level (P < 0.05) compared to the control group. These results suggestedthat OPC-21268 relieved congestive hyperemia in thegastric mucosa and ameliorated the mucosal injury causedby ethanol, probably as a result of inhibition of vasopressin-mediated actions on the stomach.The vasopressin involved was probably generated locallyin the gastric mucosa after ethanoladministration.     

Effect of Alcohol Consumption on Leptin Level in Serum, Adipose Tissue, and Gastric Mucosa

It has been reported that the stomach is a source of leptin, which is the product of the obese (ob) gene. In the present study, the effect of alcohol on leptin level in serum, gastric mucosa, and adipose tissue was studied to understand the relationship between appetite and alcohol consumption. Male Sprague-Dawley rats were administered 1 ml of 25% ethanol perorally. Leptin levels in the serum, gastric mucosa, and adipose tissue were measured. The serum leptin level was significantly decreased 3 and 6 hr after ethanol administration, although the gastric leptin level was not affected. The leptin level in the adipose tissue was significantly increased 3 hr after administration. We conclude that the decreased serum leptin level after ethanol administration might be due to suppression of leptin secretion from adipose tissue to the systemic circulation. These findings might be important for understanding the relationship between alcohol consumption and appetite.     

Reversal of ethanol and indomethacin-induced suppression of hepatic DNA synthesis by 16,16-dimethyl prostaglandin E2

Investigations were undertaken to determine effectiveness of 16,16-dimethyl prostaglandin E2 (dmPGE2) in overcoming the suppressive effects of ethanol and/or indomethacin on hepatic DNA synthesis. Adult litter mate Sprague-Dawley rats were subjected to sham operation or partial hepatectomy. Immediately after partial hepatectomy, and at 8-hr intervals for 24 hr, the rats were given: (a) ethanol with and without dmPGE2 or (b) indomethacin with and without ethanol and/or dmPGE2. DmPGE2 produced a significant increase in DNA synthesis in sham-operated (p less than 0.001) and untreated partially hepatectomized animals (p less than 0.025). Ethanol and indomethacin caused a 6- and 18-fold reduction, respectively, in hepatic DNA synthesis following partial hepatectomy. DmPGE2 overcame the inhibitory effect of ethanol (p less than 0.005) and indomethacin (p less than 0.0005) in partially hepatectomized animals. Mitoses were decreased concomitantly with ethanol and/or indomethacin-induced reduction in DNA synthesis and increased with administration of dmPGE2. It is concluded that dmPGE2 increases hepatic DNA synthesis and regeneration in normal rat liver and overcomes their inhibition when ethanol and/or indomethacin is given after partial hepatectomy. Timing of dmPGE2 administration is crucial. When given 30 min before ethanol, it completely inhibits suppression of regenerative activity; omission of this "priming" dmPGE2 dose results in only 44% of DNA synthesis obtained in control animals.     

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

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

16,16-Dimethyl prostaglandin E2 aggravates gastric mucosal injury induced by histamine in rats. Possible role of the increased mucosal vascular permeability

Histamine dihydrochloride (40 or 80 mg/kg, dissolved in 10% gelatin) subcutaneously administered to fasted rats induced few lesions in the gastric mucosa within 4 h. Pretreatment with subcutaneously administered 16,16-dimethyl prostaglandin E2 (dmPGE2; greater than or equal to 10 micrograms/kg) dose-dependently worsened mucosal injury induced by histamine, mostly with severe hemorrhage in the corpus mucosa along the greater curvature, although dmPGE2 alone did not induce any macroscopic damage. The mucosal vascular permeability as measured using Evans blue was slightly but significantly augmented by either dmPGE2 (30 micrograms/kg) or histamine (80 mg/kg) alone, but was markedly increased by histamine in the presence of dmPGE2. The increased vascular permeability occurred within 2 h, and preceded the appearance of hemorrhagic mucosal injury. Both the mucosal injury and the increased vascular permeability caused by histamine (80 mg/kg) in the presence of dmPGE2 (30 micrograms/kg) were significantly reduced by pretreatment with tripelennamine (30 mg/kg) and prednisolone (3 mg/kg), but not affected by atropine sulfate, cimetidine, methysergide, or indomethacin. The stimulation of acid secretion caused by histamine was significantly inhibited by dmPGE2 (30 micrograms/kg). Repeated administration of histamine (40 or 80 mg/kg) in the same area of the stomach in the presence of dmPGE2 (30 micrograms/kg), once or twice daily for 4 days to fed rats, induced more pronounced damage than single-dose treatment. These results suggest that dmPGE2 may aggravate gastric mucosal injury induced by histamine in rats probably due to potentiation of the increased vascular permeability caused by histamine through stimulation of H1-receptors.     

Cytoprotection by 16,16-dimethyl prostaglandin E2--role of gastric content and mucus gel layer

The mechanism of cytoprotection by prostaglandins (PGs) is still unknown, although many hypotheses have been proposed. We postulated a hypothesis that increased gastric content and thickened mucus gel layer by PGs may protect the gastric mucosa against damage from necrotizing agents. Two series of experiments were performed on Wistar male rats, weighing 250-300 g. (1) 16,16-dimethyl prostaglandin E2 (dmPGE2) in doses of 20 micrograms/kg was given orogastrically. Fifteen minutes later, the stomachs were emptied and/or the mucus gel layer removed, and several concentration of ethanol applied. After ten minutes, the stomachs were removed and lesions of the gastric mucosae were evaluated macroscopically and histologically. (2) Volume and pH of the gastric content and mucus thickness were measured 15 minutes after dmPGE2 administration. DmPGE2 did not protect the gastric mucosa against 40% ethanol in the emptied stomach. This agent had no cytoprotective action on the emptied and mucus gel-removed stomach in 30% ethanol application. These results had no significant difference with control group (saline 1 ml p.o.) about the extent of erosion. In histological study of the erosive region by scanning and light microscopy, we also found no differences in the depth of erosion between dmPGE2 group and control. In addition, dmPGE2 increased the gastric volume and mucus thickness significantly. These data suggest that following two effects by PGs play major role in cytoprotection of the gastric mucosa; (1) dilution of necrotizing agents by increased gastric content, and (2) thickening of the mucus gel layer.     

Effects of zinc sulphate on ethanol- and indomethacin-induced ulceration and changes in prostaglandin E2 and histamine levels in the rat gastric glandular mucosa

The effect of zinc sulphate on stomach ulceration produced by ethanol and indomethacin was examined in rats. Oral or intraperitoneal pretreatment with zinc sulphate (20 mg/kg, expressed as zinc ion) strongly prevented ethanol-, but not indomethacin-induced gastric glandular ulceration. Indomethacin given beforehand did not influence the protective action of zinc sulphate against ethanol-evoked lesions. Ethanol decreased histamine levels, whereas indomethacin reduced the prostaglandin E2 (PGE2) content in the gastric glandular mucosa. The alcohol also elevated the histamine content in gastric secretion. Zinc sulphate reversed the ethanol-induced changes in histamine levels in both mucosa and secretion, but did not modify PGE2 reduction by indomethacin. Zinc sulphate also antagonised protein leakage from the stomach following ethanol administration. It is concluded that gastric ulceration by the currently employed doses of ethanol and indomethacin is caused by different mechanisms. Zinc sulphate prevents histamine-mediated lesions produced by the alcohol, but not ulceration due to PGE2 depletion by indomethacin.     

Influence of prednisolone on ethanol-induced gastric injury in the rat

The purpose of the present study was to investigate the effect of prednisolone on gastric injury induced by ethanol in the rat. Gastric damage was produced by oral administration of 1 ml of absolute ethanol to rats previously fasted for 24 hr and deprived of water for 19 hr. The severity of the ethanol-induced gastric damage varied considerably within the vehicle-treated group of rats which served as controls. Prednisolone, administered orally as a single dose 15 min before alcohol challenge, significantly decreased the number of rats which developed severe lesions. Prednisolone was effective in increasing the resistance of the gastric mucosa to ethanol when given from 1 to 60 min before alcohol. The steroid proved ineffective when 90 min elapsed between prednisolone and ethanol administration, or when the steroid was given at the same time (0 min) as alcohol. The dose-response curve for prednisolone plateaued at high doses. Our results suggest that a prostaglandin-mediated endogenous cytoprotective potential exists in the rat gastric mucosa. Prednisolone may enhance the degree of mucosal protection afforded by this mechanism.     

Effect of cholecystokinin and 16,16-dimethyl prostaglandin E2 on RNA and DNA of gastric and duodenal mucosa.

Fasted rats were injected with either cholecystokinin-octopeptide (CCK-OP), 20 mug per kg; 16,16-dimethyl prostaglandin E2 (16,16-dimethyl PGE2), 0.2 mg per kg; pentagastrin, 250 mug per kg, or saline every 8 hr for 48 hr. The rats were killed and the incorporation of [3H]thymidine into DNA as well as the total DNA and RNA content of the mucosa of the oxyntic gland area and the duodenum were determined. Pentagastrin increased DNA synthesis 60% (P less than 0.001) in gastric mucosa and 90% (P less than 0.001) in duodenal mucosa when compared with rates for saline controls. Neither CCK-OP nor 16,16-dimethyl PGE2 altered gastric mucosal DNA synthesis. Pentagastrin significantly increased the DNA and RNA content of both the gastric and duodenal mucosa. CCK-OP and 16,16-dimethyl PGE2 caused a slight but significant increase in duodenal DNA synthesis, CCK-OP did not significantly increase duodenal DNA content, and 16,16-dimethyl PGE 2 increased duodenal RNA but not DNA content. CCK-OP (20 mug per kg) in combination with pentagastrin did not alter the stimulation of gastric DNA synthesis but significantly decreased the effect of pentagastrin on duodenal DNA. A dose of CCK-OP (370 mug per kg) equimolar to 250 mug per kg of pentagastrin did not stimulate DNA synthesis in either tissue and significantly inhibited stimulation by pentagastrin in both tissues. Low doses of CCK-OP (2.5, 5.0, 10.0, 20.0 mug per kg) caused statistically significant increases in DNA synthesis and DNA content of the pancreas, but had no effect on either mucosa of the oxyntic gland area or duodenum. 16,16-Dimethyl PGE2 did not inhibit the stimulation of DNA synthesis or the increases in DNA and RNA content stimulated by pentagastrin. From these results it appears that: (1) moderate doses of CCK have a weak trophic effect in the duodenum but not in the stomach, (2) physiological doses of CCK-OP stimulated pancreatic DNA synthesis and increased pancreatic DNA content without affecting these parameters in the oxyntic gland area or duodenum in the same animals, (3) in the stomach and duodenum CCK is not as potent a trophic hormone as gastrin and inhibits, probably competitively, the trophic effects of gastrin, (4) 16,16-dimethyl PGE2 does not stimulate growth and does not interfere with the trophic response to gastrin even though it inhibits acid secretion, and (5) 16,16-dimethyl PGE2 increased the RNA content of duodenal mucosa indicating that it may stimulate activity resulting in hypertrophy.     

Effect of sialoadenectomy on adaptive cytoprotection in the rat

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

Effects of nicotine and tobacco smoke on gastric secretion in rats with gastric fistulas

A light-weight plastic cannula was surgically implanted in the stomach at the nonglandular/glandular mucosal junction in male Sprague-Dawley rats. After a 3-week recovery period they were studied repeatedly over a span of 9 months. Following a 48-hr fast, gastric secretion was collected hourly for 7 hr (1 control and 6 experimental); parameters measured were gastric-juice volume (GJV), acid output (AOP), and pepsin output (POP).The effects of nicotine hydrogen tartrate and tobacco smoke in 10% ethanol saline were studied under basal conditions and after stimulation with maximal doses of histamine acid phosphate and submaximal and maximal doses of ICI-50123. In control experiments, rats received normal saline or 10% ethanol saline (tobacco smoke control).Nicotine depressed, to a varying degree, GJV and AOP in 3 hr of basal secretion; POP was unaffected. With maximal histamine-stimulated secretion, nicotine depressed GJV and AOP, to a varying degree, over the third to seventh hour; POP was depressed from the second to seventh hour. With maximal ICI-50123-stimulated secretion, nicotine depressed POP from the second to seventh hour; no effect was seen on the other parameters. With submaximal ICI-50123-stimulated secretion, POP was depressed by both nicotine and tobacco smoke; the other parameters were unaffected.Supported in part by a grant from the American Medical Association Education and Research Foundation.Thanks are due Charles A. Spezia and Manuel Angulo for technical assistance, Dr. T. Robitscher, of Ayerst Laboratories, Inc., for the ICI-50123, and Dr. Rolf Håkanson for the gastric cannulas.     

Gastroprotective activity of Nigella sativa L oil and its constituent, thymoquinone against acute alcohol-induced gastric mucosal injury in rats

AIM: To evaluate the role of reactive oxygen species in the pathogenesis of acute ethanol-induced gastric mucosal lesions and the effect of Nigella sativa L oil (NS) and its constituent thymoquinone (TQ) in an experimental model. METHODS: Male Wistar albino rats were assigned into 4 groups. Control group was given physiologic saline orally (10 mL/kg body weight) as the vehicle (gavage); ethanol group was administrated 1 mL (per rat) absolute alcohol by gavage; the third and fourth groups were given NS (10 ml/kg body weight) and TQ (10 mg/kg body weight p.o) respectively 1 h prior to alcohol intake. One hour after ethanol administration, stomach tissues were excised for macroscopic examination and biochemical analysis. RESULTS: NS and TQ could protect gastric mucosa against the injurious effect of absolute alcohol and promote ulcer healing as evidenced from the ulcer index (UI) values. NS prevented alcohol-induced increase in thiobarbituric acid-reactive substances (TBARS), an index of lipid peroxidation. NS also increased gastric glutathione content (GSH), enzymatic activities of gastric superoxide dismutase (SOD) and glutathione-S-transferase (GST). Likewise, TQ protected against the ulcerating effect of alcohol and mitigated most of the biochemical adverse effects induced by alcohol in gastric mucosa, but to a lesser extent than NS. Neither NS nor TQ affected catalase activity in gastric tissue. CONCLUSION: Both NS and TQ, particularly NS can partly protect gastric mucosa from acute alcohol-induced mucosal injury, and these gastroprotective effects might be induced, at least partly by their radical scavenging activity.     

Increased susceptibility of ethanol-treated gastric mucosa to naproxen and its inhibition by DA-9601, an Artemisia asiatica extract

AIM: To examine the effect of DA-9601, a new gastroprotective agent, on the vulnerability of ethanol-treated rat's stomach to naproxen (NAP). METHODS: Male Sprague-Dawley rats were pretreated with 1 mL of 50% ethanol twice a day for 5 d and then NAP (50 mg/kg) was administered. DA-9601 was administered 1 h before NAP. Four hours after NAP, the rats were killed to examine gross injury index (mm2), histo-logic change and to determine mucosal levels of malo-ndialdehyde (MDA), prostaglandin E2 (PGE2), glutathione (GSH) and myeloperoxidase (MPO). RESULTS: Pretreatment of ethanol significantly increased NAP-induced gastric lesions, as well as an increase in MDA and MPO. On the contrary, mucosal PGE2 and GSH contents were decreased dramatically by ethanol pretreatment, which were aggravated by NAP. DA-9601 significantly reduced NAP-induced gastric injury grossly and microscopically, regardless of pretreatment with ethanol. DA-9601 preserved, or rather, increased mucosal PGE2 and GSH in NAP-treated rats (P<0.05), with reduction in mucosal MDA and MPO levels. CONCLUSION: These results suggest that repeated alcohol consumption renders gastric mucosa more susceptible to NSAIDs though, at least in part, reduction of endogenous cytoprotectants including PGE2 and GSH, and increase in MPO activation, and that DA-9601, a new gastroprotectant, can reduce the increased vulnerability of ethanol consumers to NSAIDs-induced gastric damage via the mechanism in which PGE2 and GSH are involved.     

Histologic and microcirculatory changes in alcohol-induced gastric lesions in the rat: effect of prostaglandin cytoprotection

The effect of 16,16-dimethyl prostaglandin E2 (dmPGE2) on histologic and microcirculatory changes in alcohol-induced gastric mucosal injury was studied. A histologic study confirmed that dmPGE2 does not protect the surface mucous cells against ethanol injury but does protect against the deeper necrotic lesion. Both the gross injury and the necrotic lesion were as severe after 1 min of ethanol exposure as after 60 min. A study of benzidine-stained sections and hematoxylin and eosin-stained sections revealed marked engorgement of microvessels and hemorrhage in the superficial mucosa after ethanol injury. Pretreatment with dmPGE2 prevented these. An in vivo fluorescent microscopy study revealed that there was total stasis of blood flow in the injured area. After the intravascular injection of a fluorescein-albumin conjugate, the conjugate filled microvessels in grossly normal areas of mucosa but not in grossly injured areas. Pretreatment with dmPGE2 prevented this microcirculatory change. This alcohol-induced stasis of flow in injured areas may be of pathogenetic significance and prostaglandin protection might involve prevention of this microcirculatory change.     

Morphological and functional gastric cytoprotection by prostaglandin in rats receiving absolute ethanol orally.

Pretreatment with prostaglandins at non-antisecretory doses protects the gastric mucosa, including the parietal cells, from deep necrosis produced by intragastric administration of necrotising agents such as absolute ethanol. Whether the parietal cells also retained their ability to secrete acid when rats were pretreated with a prostaglandin, in spite of exposure to ethanol, was investigated. Gastric acid secretion was abolished 4 hours after ethanol, and secretion returned to control values only after 5-6 days. Pretreatment with a single, non-antisecretory dose of 16, 16-dimethyl prostaglandin E2 (dm PGE2) maintained acid secretion, in spite of exposure to absolute ethanol. Absolute ethanol caused histological changes - extensive gastric mucosal necrosis (through the muscularis mucosae), oedema, haemorrhages, polymorphonuclear infiltration, and formation of granulation tissue - that were maximal 24-48 hours after ethanol and persisted for 2 to 4 weeks. None of these changes were present in animals treated with the prostaglandin. It is concluded that a single oral pretreatment with dmPGE2 protects the gastric mucosa against not only the morphological damage of absolute ethanol (preventing necrosis, haemorrhages, and polymorphonuclear infiltration) but also the functional damage (maintaining the acid secretory function of parietal cells).     

Cytoprotective and ulcer healing properties of prostaglandin E2, colloidal bismuth and sucralfate in rats

This study describes the model of chronic gastric and duodenal ulcerations induced by the application of acetic acid on a strictly defined area of the serosal surface of the stomach and duodenum for 10 and 20 s, respectively. Acetic acid applied for longer (20-60 s) or on a larger area (28-64 mm2) resulted in the formation of severe ulcerations which penetrated into the surrounding organs and had very prolonged healing time. Ulcers induced by the application of acetic acid for 10-20 s on a smaller area (7-13.8 mm2) healed spontaneously within 2-3 weeks, thus constituting a model suitable for evaluation of drugs affecting the process of ulcer healing. Our preliminary results of 7- to 14-day treatment with certain drugs indicate that sucralfate and De-Nol, at the dose which does not affect gastric acid secretion, accelerated the healing rate of both gastric and duodenal ulcers so that the observed ulcer healing effect could be attributed to their ulcer healing property. In contrast, 16, 16-dimethyl PGE2 (dmPGE2) in cytoprotective dose was completely ineffective in enhancing ulcer healing. Higher, gastric inhibitory dose of dmPGE2 accelerated the healing of duodenal but not gastric ulcerations, indicating that the inhibition of gastric secretion rather that cytoprotective activity is responsible for ulcer healing effect of this prostaglandin.     

Augmentative effects of L-cysteine and methylmethionine sulfonium chloride on mucin secretion in rabbit gastric mucous cells

BACKGROUND: Our previous study showed that L-cysteine (Cys) and methylmethionine sulfonium chloride (MMSC) inhibited ethanol-induced gastric mucosal damage and increased the amount of surface mucin in rats. This study examined whether Cys and MMSC augmented mucin secretion and changed distribution of mucin vesicles ultrastructurally in mucous cells by using primary cultured mucous cells from rabbit glandular stomach. Changes in intracellular cyclic adenosine 3',5'-monophosphate (cAMP) and in levels of cytosolic free Ca2+ were investigated by treatment with Cys and MMSC. METHODS: Mucin content was measured by an enzyme-linked lectin assay. Transmission electron micrography was used to examine ultrastructural distribution of mucin granules. The amount of cAMP or levels of free Ca2+ were measured by enzyme immunoassay or by fura-2. 16,16-Dimethyl prostaglandin E2 (dmPGE2) or ATP was used as the positive control. RESULTS: L-Cysteine and MMSC increased mucin secretion and decreased cellular mucin content. The same was noted for dmPGE2. Accelerated mucin granule movements toward the plasma membrane were shown by these agents. Intracellular cAMP increased with exposure to dmPGE2 for 20 min, while neither Cys nor MMSC increased cAMP. No increase in cytosolic free Ca2+ levels occurred after treatment with Cys or MMSC, but an increase was induced 10 s after the addition of ATP. CONCLUSIONS: The present findings indicate that the increase in mucin secretion by Cys and MMSC was not mediated through the cAMP or Ca2+ signal transduction pathway, but might occur through non-receptor-mediated mechanisms.     

Gastric metabolism of ethanol in Syrian golden hamster

First-pass metabolism (FPM) of orally ingested alcohol has been attributed to gastric alcohol dehydrogenase (ADH) activity in both humans and rats. To determine whether gastric alcohol dehydrogenase is essential for alcohol FPM, we sought a species lacking this enzyme. We found that Syrian golden hamsters have negligible gastric ADH yet alcohol FPM (265±25 mg ethanol/kg) was comparable to that of rats (251±31 mg/kg). To determine whether hamster gastric mucosal cells metabolize sufficient alcohol to account for this FPM, primary cultures were established, and these cells metabolized 1.99±0.84 mol ethanol/10⁶ cells/hr, an amount sufficient to account for the bulk of alcohol FPM. In contrast to alcohol dehydrogenase, catalase activity in hamster gastric mucosa (870±93 units/g tissue) was eightfold higher than in rat gastric mucosa (111±9 units/g tissue;P<0.0001). FPM in hamsters treated with 3-aminotriazole was reduced from 242±24 to 130±22 mg/kg (P<0.05) but was not reduced in rats. The results imply that catalase participates in gastric alcohol metabolism of hamsters.Supported by NIH grants AA03508 and AA07275 and the Department of Veteran Affairs.     

Gastric mucosal ulceration following vasoactive agents

The influence of the vasoactive catecholamines, epinephrine and norepinephrine, has been investigated in regard to the comparative ulcerogenicity on the gastric glandular mucosa of the rat. The unique extensive, hemorrhagic necrosis, and ulcerations which appear in the fundus—but not the antrum—following single injections of these drugs are readily quantified because of the continuous nature of the lesion. A standard assay has been developed with this new ulcer model, which results in extensive mucosal ulceration (43% of fundus with lesions) in 100% of treated animals after only 5 hr. The optimal procedure requires the single intraperitoneal epinephrine injection of 0.4 mg/kg to young adult Sprague-Dawley rats 4 hr after pylorus occlusion, and the sacrifice of animals 1 hr after injection. This experimental gastric lesion is dependent upon the presence of gastric acid, and is completely inhibited by bilateral vagotomy, and almost completely inhibited by the presence of a magnesium-aluminum hydroxide gel-type antacid.