Effects of tetragastrin on mucus glycoprotein in rat gastric mucosal protection.

The effects of tetragastrin on mucus glycoprotein (mucin) metabolism and mucosal protection in rat gastric mucosa were investigated. Rats were administered with various doses of tetragastrin (12, 120, or 400 micrograms/kg body weight; s.c.), followed by 50% ethanol-induced gastric injury. Tetragastrin caused a significant increase in mucin content in the corpus mucosa and prevented 50% ethanol-induced gastric mucosal damage in a dose-dependent manner. For assessment of the effects of tetragastrin on the metabolism of gastric mucin in detail, changes in mucin distribution in the three different layers of rat gastric mucosa were examined one hour after single administration of tetragastrin. A significant increase in the mucin content was noted in the mucus gel and surface mucosal layer. Mucin content in the deep mucosa corresponding mainly to the mucus neck cell mucin underwent virtually no change by this treatment. An increase in mucin in the mucus gel and surface mucosa would thus appear due to the administration of tetragastrin and may possibly be related to the protective action of the gastric mucosa against injury. The data demonstrate a possibility that gastrin may have potential for enhancing gastric mucosal protection associated with mucus secretion and/or mucus synthesis on the surface mucosa of rat gastric mucosa.     

Effects of the Mt Muscarinic Receptor Antagonist Pirenzepine on Gastric Mucus Glycoprotein in Rats with or without Ethanol-Induced Gastric Damage

Changes in gastric mucus glycoprotein (mucin) isolated from pirenzepine-treated rats with or without ethanol (50%)-induced gastric damage were studied. The prior administration of pirenzepine inhibited significantly and dose-dependently the occurrence of macroscopically observable hemorrhagic lesions induced by treatment with ethanol. The gastric mucosa was separated into the surface mucosa, including the mucus gel layer, and the deeper mucosa by mechanical scraping, and the mucin in each was isolated. In cthanol-treated animals the mucin content of the deep corpus mucosa was significantly reduced to 68% the control value. This reduction was inhibited by pretreatment with pirenzepine. In the surface mucosa mucin content was also reduced to 48% of control value by ethanol treatment, but pirenzepine pretreatment increased mucin content to 235% the control value. Total mucin content in the entire stomach essentially resumed the control level by pretreatment with 100 mg/kg of pirenzepine. A single oral administration of pirenzepine (100 mg/kg) caused no change in total mucin content, but mucin in the deep corpus mucosa selectively and significantly increased to 124% the control. These and the results of carbohydrate analysis of purified mucin indicate that pirenzepine administration possibly accelerates the secretion of accumulated deep corpus mucus, retains this deep mucus on surface mucosal mucus, and protects the gastric mucosa in ethanol-induced gastric damage. This may be related to the antiulcerogenic effects of pirenzepine.     

Effects of the M1 muscarinic receptor antagonist pirenzepine on gastric mucus glycoprotein in rats with or without ethanol-induced gastric damage.

Changes in gastric mucus glycoprotein (mucin) isolated from pirenzepine-treated rats with or without ethanol (50%)-induced gastric damage were studied. The prior administration of pirenzepine inhibited significantly and dose-dependently the occurrence of macroscopically observable hemorrhagic lesions induced by treatment with ethanol. The gastric mucosa was separated into the surface mucosa, including the mucus gel layer, and the deeper mucosa by mechanical scraping, and the mucin in each was isolated. In ethanol-treated animals the mucin content of the deep corpus mucosa was significantly reduced to 68% the control value. This reduction was inhibited by pretreatment with pirenzepine. In the surface mucosa mucin content was also reduced to 48% of control value by ethanol treatment, but pirenzepine pretreatment increased mucin content to 235% the control value. Total mucin content in the entire stomach essentially resumed the control level by pretreatment with 100 mg/kg of pirenzepine. A single oral administration of pirenzepine (100 mg/kg) caused no change in total mucin content, but mucin in the deep corpus mucosa selectively and significantly increased to 124% the control. These and the results of carbohydrate analysis of purified mucin indicate that pirenzepine administration possibly accelerates the secretion of accumulated deep corpus mucus, retains this deep mucus on surface mucosal mucus, and protects the gastric mucosa in ethanol-induced gastric damage. This may be related to the antiulcerogenic effects of pirenzepine.     

Distinct Effects of Tetragastrin in Rat Gastroduodenal Mucosa on Mucin Content and Mucosal Protective Action Against Histamine-Induced Injury

We examined the effects of tetragastrin on mucin(mucus glycoprotein) content and mucosal damage in therat stomach and duodenum. Following an injection oftetragastrin (12, 120, or 400 g/kg subcutaneously), no macroscopic damage was found to the gastricmucosa but an increase in corpus mucin content wasnoted, whereas mucosal lesions appeared and the mucincontent decreased in the duodenum in a dose-related manner. In the groups with histamine (0.8, 8,or 80 mg/kg intraperitoneally) administration, theextent of mucosal damage and the decrease in mucincontent were dose-related in both these regions. Forassessment of the effect of tetragastrin on the protectiveaction in gastroduodenal mucosa, changes in mucincontent and mucosal damage with histamine (80mg/kg)-induced injury were examined. Coadministration oftetragastrin prevented the gastric mucosal damage andinhibited the decrease in corpus mucin content. In theduodenum, tetragastrin aggravated the histamineinducedmucosal damage and did not inhibit the reduction of the mucin content. From the present results,the increase in gastric mucins induced by tetragastrinmight be related to the protective effect of gastricmucosa against injury. Tetragastrin did not protect the duodenal mucosa, and histamine-inducedinjury occurring in this region would be aggravated bythe increase in HCl secretion and the decrease in mucincontent induced by tetragastrin.     

Recovery of mucin content in surface layer of rat gastric mucosa after HCl-aspirin-induced mucosal damage

Quantitative changes in mucin (mucus glyco-protein) in different layers of rat gastric mucosa after mucosal damage induced by acidified acetylsalicylic acid (HCl-aspirin; 0.15N HCl, 20–200 mg acetylsalicylic acid/kg body weight) were studied. More than 50 mg/kg HCl-aspirin led to a significant increase in macroscopic gastric injury (expressed as ulcer index) at 3h, compared with control (no aspirin) and there was a significant recoverly at 7h. Three h after dosing with 50 mg/kg acidified aspirin, there was superficial mucosal damage and decreased mucin content in the surface mucosal layer. Mucin production recovered 7h after the administration of 50 mg/kg acidified aspirin. Doses of acidified aspirin higher than 100 mg/kg decreased mucin content in the surface and deep corpus mucosal layers and no recovery was seen 7h after the administration. Physiological damage after the administration of 50 mg/kg HCl-aspirin was limited mainly to surface epithelial mucus cells. An experimental model in which superficial erosion was induced in rat gastric mucosa was established with low-dose HCl-aspirin.     

A separating method for quantifying mucus glycoprotein localized in the different layer of rat gastric mucosa

A method was devised for separating rat gastric mucosa into three layers each containing a different mucin species. The mucus gel (first layer) was removed by stirring the gastric mucosa in a solution of phosphate-buffered saline containing 2% N-acetylcysteine. The surface mucosa (second layer), rich in surface mucus cells, was then separated from the deep mucosa (third layer) containing mucus neck cells, by scraping with forceps. The effectiveness of this method was confirmed by light microscopical observation after GOCTS-PCS (dual staining by the galactose oxidase-cold thionin Schiff method and paradoxical concanavalin A method) and AB-PAS staining (dual staining with alcian blue and the periodic acid Schiff method). The fixed specimen of scraped mucus and cell debris was rich in AB-PAS and GOCTS positive mucus, but was hardly stained by PCS, indicating mucus derived from surface mucus cells to have been efficiently recovered from this preparation. The residual mucosa could be stained by PCS but hardly at all by AB-PAS or GOCTS. The lyophilized powder specimens obtained from the three different layers of rat gastric mucosa were used to extract and quantify mucus glycoprotein (mucin). This was done to examine changes in mucin content in the three layers of gastric mucosa one hour following the oral administration of 20% ethanol or 0.35 N hydrochloric acid, both mild irritants. Mucin content was noted to significantly increase in the first layer but hardly at all in the second layer. In the third layer, it decreased significantly by 0.35 N hydrochloric acid, but changed only slightly by 20% ethanol administration. This method is thus shown to be suitable for detecting changes in the gastric mucin content in each of the three separate layers of gastric mucosa. This work was supported in part by Grants-in-Aid from the Japa nese Ministry of Education and Terumo Life Science Foundation. The authors express their sincere appreciation to Prof. Haruya Okabe for his valuable comments.     

Effects of a novel histamine H2-receptor antagonist, lafutidine, on the mucus barrier of human gastric mucosa

BACKGROUND AND AIM: Lafutidine is a novel histamine H(2)-receptor antagonist used primarily as an antisecretory agent in Japan. Previous human studies have not assessed its gastroprotective effects. The purpose of the present study was to determine the effects of lafutidine on the human gastric mucus layer using both histological and biochemical methods. METHODS: Of the 14 patients scheduled for gastrectomy who consented to participate, seven were given 14 days of lafutidine 20 mg/day (lafutidine group) and the others received no medication (control group). The surface mucus gel layer in Carnoy-fixed tissue sections was examined immunohistochemically. Both the thickness of the mucus layer and its mucin content were measured in gastric corpus mucosa. RESULTS: There was no detectable difference between the groups in the grade of gastritis or the immunohistochemical staining characteristics. The laminated structure of the surface mucus gel layer was retained after administration of lafutidine and it was thicker than the layer in the control group. The surface layer in the lafutidine group had three-fold more mucin than that in the control group. There was no difference between the two groups in the mucin content of the deep mucosa. CONCLUSION: Lafutidine, given at clinical dosages, not only inhibits acid secretion but also strengthens the mucus barrier of the human gastric mucosa.     

Effects of combination treatment with famotidine and methylmethionine sulfonium chloride on the mucus barrier of rat gastric mucosa

Background and Aim:  In Japan, peptic ulcer disease (PUD) is treated clinically with a combination of a mucosal protectant and acid suppressants, but there is scant information regarding the effects of these drugs on normal gastric mucus cells. In the present study, the effects of co-administration of methylmethionine sulfonium chloride (MMSC) and famotidine on rat gastric mucus cells were investigated using both biochemical and histological methods.
Methods:  Rats were divided into four groups: controls were given carboxymethylcellulose orally once daily for 7 days and the second, third and fourth groups were treated similarly with famotidine (famotidine group), MMSC (MMSC group) or famotidine plus MMSC (combination group). After killing the rats on the 8th day, the stomachs were removed and the biosynthesis and amount of mucin in different areas of the gastric mucosa were compared among groups. Using anti-mucin monoclonal antibodies, the mucin content and immunoreactivity were also compared.
Results:  Both the biosynthesis and accumulation of mucin were significantly decreased in the famotidine group, but increased in the MMSC and combination groups. The amount and immunoreactivity of surface mucus cell-derived mucin were both reduced in the famotidine group, and increased in the MMSC and combination groups. There was no difference among the groups in the content and immunoreactivity of gland mucus cell-derived mucin.
Conclusion:  Famotidine-induced suppression of gastric surface mucus cell function is prevented by combined treatment with MMSC, raising the possibility of a more effective cure of PUD.     

Restorative Impact of Rabeprazole on Gastric Mucus and Mucin Production Impairment During Naproxen Administration: Its Potential Clinical Significance

Rabeprazole augments gastric mucus and mucin production in humans. However, its potential restorative impact on gastric mucus and mucin production impairment, resulting from administration of naproxen, remained to be explored. Therefore, we measured the content of mucus and mucin in gastric juice (GJ) before and after administration of naproxen with rabeprazole or placebo. The study was approved by HSC at KUMC and conducted in 21 asymptomatic, H. pylori–negative volunteers in a double-blind, placebo-controlled, crossover design. The content of gastric mucus in GJ, after exhaustive dialysis and complete lyophilization, was assessed gravimetrically, whereas the content of mucin was measured after its purification with equilibrium density-gradient ultracentrifugation in CsCl. Gastric mucus secretion during administration of naproxen with placebo declined significantly both in basal (by 44%; P < 0.001) and in pentagastrin-stimulated (by 35%; P < 0.001) conditions. Coadministration of rabeprazole significantly restored the naproxen-induced impairment in mucus production in basal conditions (by 47%; P < 0.01) and by 22% during stimulation with pentagastrin. Gastric mucin secretion during naproxen/placebo administration also declined significantly in both basal (by 39%; P < 0.01) and stimulated (by 49%; P = 0.003) conditions. Rabeprazole also significantly restored the naproxen-induced decline of gastric mucin output during pentagastrin-stimulated conditions (by 67%; P = 0.003) and by 40% in basal conditions (P = 0.05). The restorative capacity of rabeprazole on the quantitative impairment of gastric mucus and mucin during administration of naproxen may translate into a clinical benefit of protection of the upper alimentary tract from NSAID-related mucosal injury.     

A separating method for quantifying mucus glycoprotein localized in the different layer of rat gastric mucosa.

A method was devised for separating rat gastric mucosa into three layers each containing a different mucin species. The mucus gel (first layer) was removed by stirring the gastric mucosa in a solution of phosphate-buffered saline containing 2% N-acetylcysteine. The surface mucosa (second layer), rich in surface mucus cells, was then separated from the deep mucosa (third layer) containing mucus neck cells, by scraping with forceps. The effectiveness of this method was confirmed by light microscopical observation after GOCTS-PCS (dual staining by the galactose oxidase-cold thionin Schiff method and paradoxical concanavalin A method) and AB-PAS staining (dual staining with alcian blue and the periodic acid Schiff method). The fixed specimen of scraped mucus and cell debris was rich in AB-PAS and GOCTS positive mucus, but was hardly stained by PCS, indicating mucus derived from surface mucus cells to have been efficiently recovered from this preparation. The residual mucosa could be stained by PCS but hardly at all by AB-PAS or GOCTS. The lyophilized powder specimens obtained from the three different layers of rat gastric mucosa were used to extract and quantify mucus glycoprotein (mucin). This was done to examine changes in mucin content in the three layers of gastric mucosa one hour following the oral administration of 20% ethanol or 0.35 N hydrochloric acid, both mild irritants. Mucin content was noted to significantly increase in the first layer but hardly at all in the second layer. In the third layer, it decreased significantly by 0.35 N hydrochloric acid, but changed only slightly by 20% ethanol administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intragastric nicotine protection against 40% ethanol injury in rat stomach

Intragastric nicotine (4 mg/kg) protects against 40% ethanol-induced gastric mucosal injury and raises mean blood pressure. We postulated that this protective effect was mediated by the ganglionic stimulatory property of nicotine and therefore could be abolished by ganglionic blockers. Rats were pretreated with intraperitoneal hexamethonium (10 mg/kg) or mecamylamine (2 mg/kg) to block peripheral or central autonomic ganglia, respectively. Intragastric vehicle or nicotine (4 mg/kg) was then administered. The total lengths of the linear gastric corpus mucosal lesions induced by intragastric 40% ethanol were measured by an unbiased observer using a caliper. The results showed that both intraperitoneal hexamethonium and mecamylamine pretreatments protected against 40% ethanol-induced gastric mucosal injury. Neither modified the protective effect of intragastric nicotine. The protective effect of hexamethonium and mecamylamine was associated with a significant increase in the volume of gastric mucus and gastric juice. The increase in the volume of gastric content (mucus and juice) was partially responsible for the protective effect of these ganglionic blockers. In a separate experiment, intraperitoneal nicotine (4 mg/kg) also protected against 40% ethanol-induced gastric mucosal injury and raised mean blood pressure. These data indicate that the protection against 40% ethanol-induced gastric mucosal injury is not unique to intragastric nicotine. Such protection can be induced by ganglionic blocking doses of hexamethonium and mecamylamine, or a ganglionic stimulatory dose of intraperitoneally administered nicotine. Whether ganglionic stimulation or blockade plays a role in the mechanism of intragastric nicotine protection, however, remains to be determined. Further studies of the regulation of gastric mucus production and gastric juice volume may shed light on the mechanism of protection afforded by intragastric nicotine.Supported by Veterans Administration Medical Research Funds, and in part by research grants (0162-01, 0162-02 and 0291-01) from the Smokeless Tobacco Research Council, Inc., and by funds (IRT 80) provided by the Cigarette and Tobacco Surtax Fund of the State of California through the Tobacco-Related Disease Research Program of the University of California to F.W.L. Dr. Endoh is a recipient of the University of California Tobacco-Related Disease Research Program Research Fellowship Award (FT 37).     

A new method of separation and quantitation of mucus glycoprotein in rat gastric mucus gel layer and its application to mucus secretion induced by 16,16-dimethyl PGE2

A method was established for recovering the mucus gel layer of rat gastric mucosa without damage to underlying surface epithelium. The mucus gel was solubilized by stirring the gastric mucosa in a solution of N-acetylcysteine (NAC), a mucolytic agent. Optimal mucus gel solubilization was possible by treatment with 2% NAC for 5 minutes at room temperature. Mucus glycoprotein was quantitatively extracted and measured from the mucus gel sample obtained by the NAC treatment. This treatment caused no damage to surface epithelial cells, as observed by a light microscope. Besides NAC, pronase solution was also adequate for solubilizing the mucus gel layer without any damage to the surface epithelium. However, extraction and measurement of mucus glycoprotein from the pronase-treated mucus gel sample was not possible due to contamination by high molecular hexose-containing substances which were eluted along with the mucus glycoprotein from the column of Bio-Gel A-1.5m. This NAC method was used to examine changes in mucus glycoprotein content in the mucus gel at one hour following the oral administration of 16,16-dimethyl prostaglandin E₂. A significant increase in mucus glycoprotein of the gel was brought about by the prostaglandin treatment. Thus, the present method was suitable for estimating the amount of mucus secreted in to the mucus gel layer. This work was supported in part by Grants-in-Aid from the Japanese Ministry of Education. The authors express their sincere appreciation to Prof. Haruya Okabe for his valuable comments and encouragement throughout this study. They are also grateful to Dr. Tsuto mu Katsuyama for his valuable comments.     

Effects of acid secretagogues on rat gastric mucus glycoprotein content and gastric mucosal resistance

In our previous reports, low dose acid secretagogues caused increase in corpus mucus glycoprotein content in rats. This increase was not due to the direct action of protons. The present study was conducted to determine whether this increase has a mucosal function or not Rats were given histamine (0.8 mg/kg) intraperitoneally or tetragastrin (12 micrograms/kg) subcutaneously. One hour following the acid secretagogues administration, the animals were given 1 ml of 30, 40 or 50% ethanol orally and then sacrificed after one hour. Gastric mucus glycoproteins were isolated from the corpus region of stomach. The following results were obtained: 1) Histamine prevented the gastric mucosal damage and the decrease of corpus mucus glycoprotein content induced by 40% ethanol ingestion. 2) Tetragastrin prevented the gastric mucosal damage induced by 30 approximately 50% ethanol ingestion and the decrease of corpus mucus glycoprotein content induced by 40 approximately 50% ethanol ingestion. Based on these results, the increase of corpus mucus glycoprotein content induced by acid secretagogues has a mucosal function. Moreover, tetragastrin strengthened the mucosal defence together with acid secretion.     

Nature of the enhancement of the protective qualities of gastric mucus by sucralfate

The effects of intragastric administration of an antiulcer drug, sucralfate, on the content, composition and physical properties of the mucus component of gastric mucosal barrier were investigated. The experiments were conducted with two groups of rats in which one group received twice daily for five consecutive days a dose of 100 mg sucralfate, while the control group received daily doses of saline. The animals were sacrificed 16 h after the last dose, their stomachs dissected and the mucosa subjected to measurements of the adherent mucus gel dimension and mucin content, evaluation of its viscosity, H+ retardation capacity and hydrophobicity, and analysis of its components and molecular form distribution of elaborated mucin. The results revealed that sucralfate elicited only a minor (8%) increase in mucus gel dimension, while sulfo- and sialomucin contents of the gel increased by 63 and 81%, respectively. The changes in mucus gel mucin content with sucralfate were accompanied by a slight (9.5%) increase in mucus H+ retardation capacity, 1.9-fold increase in viscosity, and a 60% increase in the gel hydrophobicity. Chemical analyses indicated that the mucus elaborated in the presence of sucralfate exhibited 14% lower protein content and 62% higher content of carbohydrate than that of control, displayed similar levels of total lipids and covalently bound fatty acids, but its neutral lipid content was significantly higher. Furthermore, the gastric mucus of the sucralfate group showed a marked increase in the proportion of the high-molecular-weight form of mucin, while the low-molecular-weight form predominated in the control group. The results indicate that the protective qualities of sucralfate lie mainly in its ability to enhance the gastric mucus gel viscosity, hydrophobicity, content of mucin and its proportion in the high-molecular-weight form.     

Mechanism of intragastric nicotine protection against ethanol-induced gastric injury

To elucidate the mechanism of intragastric nicotine protection against ethanol-induced gastric mucosal injury seen in a previous report and in our preliminary study, the following studies were performed. Rats were pretreated with naloxone (8 mg/kg intraperitoneal, 0.5 hr prior to study) to block opiate receptors; or capsaicin (125 mg/kg subcutaneous 10 days prior to study) to denervate the afferent sensory fibers; or indomethacin (2.5 mg/kg intragastric or 5 mg/kg subcutaneous, 1 hr prior to study) to inhibit endogenous prostaglandin synthesis. At 1-hr intervals, nicotine (4 mg/kg) or vehicle and 40% ethanol were then given intragastrically. Total gastric corpus mucosal lesion length was measured unbiasedly. In separate studies, gastric mucosal blood flow (GMBF) was assessed by hydrogen gas clearance before and after intragastric nicotine or vehicle; luminal mucus volume, gastric juice volume, and acid output were measured 1 hr after either intragastric nicotine or vehicle administration. The results showed that the acute protective effect of intragastric nicotine was associated with a significantly larger luminal mucus volume. It was not blocked by naloxone, capsaicin, or indomethacin. There was no increase in GMBF. The larger gastric residual volume did not account for the protection. We conclude that the mechanism mediating nicotine protection is unique and is independent of opiate receptors, capsaicin-sensitife afferent sensory nerve fibers, endogenous prostaglandin generation, or dilution of the injurious agent. The increase in luminal gastric mucus volume may contribute to the protective effect of intragastric nicotine against gastric mucosal injury produced by 40% ethanol.     

Misoprostol-induced increases in adherent gastric mucus thickness and luminal mucus output

Gastroduodenal mucus can be separated into two phases: insoluble mucus gel adherent to the mucosal surface, and luminal mucus, which is removed by washing out the lumen. The adherent mucus gel is part of the mucosal protective barrier to acid and pepsin in the gastric juice. Luminal mucus, which is mobile, probably does not significantly protect against gastric juice, but functions as a lubricant, protecting the adherent mucus layer and underlying mucosa from mechanical damage. Adherent mucus is observed on the mucosal surface as a thin, continuous, gelatinous layer of variable thickness, about 50–450 μm (median, 180 μm) in man and 10–230 μm (median 80 μm) in the rat. Thickness of this adherent mucus layer in the rat stomach is increased significantly (up to threefold) following topical administration of misoprostolin vivo 1 hr before measurement. Simultaneous increases are observed in the content of luminal mucus following misoprostol administration. Seventy percent of maximum response is observed within 5 min of topical prostaglandin administration, compatible with the release of preformed mucus. Such prostaglandin-stimulated increases in mucus thickness will improve the protective capacity of the adherent mucus gel. The thickness of the adherent mucus layer is not changed following topical exposure,in vivo 1 hr before measurement, to exogenous mucosal-damaging agents (eg, ethanol, indomethacin and taurocholate). However, since such damaging agents permeate the mucus gel, it appears to offer little initial protection to the underlying epithelium. The mucus barrier primarily guards against the natural aggressors acid and pepsin, protecting the epithelium and its repair following acute mucosal damage.     

Trefoil factor 2 in gland mucous cell mucin in the mucous gel covering normal or damaged gastric mucosa using the Mongolian gerbil model

OBJECTIVE: Trefoil factor 2 (TFF2) is localized in gastric gland mucous cells. The purpose of the study was to determine whether TFF2 and gastric mucin are localized in mucous cells and in the surface mucous gel layer (SMGL) of the normal gastric mucosa or in the mucoid cap adherent to gastric mucosal lesions in Mongolian gerbils. MATERIAL AND METHODS: Gastric mucosal lesions were induced in Mongolian gerbils using oral administration of Helicobacter pylori (H. pylori), subcutaneous administration of indomethacin, or oral administration of 30% ethanol. Tissue samples were fixed in Carnoy's solution for preservation of the SMGL, dehydrated, and embedded in paraffin. Histochemical staining for gastric mucins and immunostaining for TFF2 were performed. RESULTS: It was found that surface mucous cell mucin and gland mucous cell mucin were segregated in the SMGL covering the normal gastric mucosa, and the mucin of the mucoid cap covering the mucosal lesions was primarily gland mucous cell mucin. There was a co-localization of TFF2 in gland mucous cell mucin in gland mucous cells, the SMGL, and the mucoid cap. CONCLUSIONS: The co-localization of TFF2 in gland mucous cells and in the adherent mucus suggests a physical interaction between TFF2 and gland mucous cell mucin, and the participation of TFF2 trapped in the adherent mucus functions in mucosal defense, healing, and repair.     

Circadian rhythms of gastric mucus efflux and residual mucus gel in the fasting rat stomach

We hypothesized that two putative gastric protective factors, mucus efflux and residual mucus gel content, would manifest circadian rhythms, as reported in several other gastric functions. Rats were adapted for three weeks on a 12-hr light schedule, fasted 18-hr and studied at 3-hr intervals. Under anesthesia, the stomachs were cannulated and filled with test solution. Thirty minutes later, they were drained and the luminal fluid was analyzed for mucus content by Alcian blue binding. Residual mucus gel was determined by direct injection of dye into the lumen. Alcian blue binding of rat mucus was expressed as equivalent milligrams of porcine mucin. Both parameters showed a significant (P<0.001) circadian rhythm. Mucus efflux peaked at 5:03±0:52 HALO (hours after lights on), and residual mucus at 6:00±0.46 HALO. Thus, the interplay of circadian rhythms in aggressive and defensive gastric mucosal functions is supported.     

Protection against alcohol-induced gastric mucosal injury by geranylgeranylacetone: effect of indomethacin

The mechanism of gastric mucosal protection by an antiulcer agent, geranylgeranylacetone (GGA), against ethanol-induced injury was investigated. The experiments were conducted with groups of rats with and without intraperitoneal indomethacin pretreatment. Animals received intragastrically either a dose of GGA (200 mg/kg) or a vehicle, followed 30 min later by 1 ml of absolute ethanol. The rats were sacrificed after 30 min and the gastric mucosa was subjected to macroscopic and histologic assessment and the measurements of adherent mucus, its dimension and chemical composition. In the absence of GGA, ethanol produced advanced macroscopic necrosis (greater than 38%) and the extensive necrotic lesions were visible upon histologic examination. Pretreatment with GGA significantly reduced (p less than 0.001) the extent and depth of mucosal necrotic lesions caused by ethanol, and this protection was not thwarted by indomethacin. Evaluation of the adherent mucus and its dimension by Alcian blue uptake and inverted microscope technique revealed that GGA was also capable of preventing the untoward effect of indomethacin on the adherent gastric mucus gel and its thickness. Results of chemical analyses established that in the absence of GGA indomethacin caused an increase in mucus protein (15%) and a decrease in its covalently bound fatty acids (67%) and lipids (36%). The decrease in lipids was particularly reflected in the content of phospholipids. Indomethacin, however, had no apparent effect on the composition of gastric mucus elaborated in the presence of GGA. The results suggest that gastric mucosal protective action of GGA is not mediated by endogenous prostaglandins but rather appears to involve the metabolism of mucosal lipids.     

Trefoil factor 2 in gland mucous cell mucin in the mucous gel covering normal or damaged gastric mucosa using the Mongolian gerbil model

Objective. Trefoil factor 2 (TFF2) is localized in gastric gland mucous cells. The purpose of the study was to determine whether TFF2 and gastric mucin are localized in mucous cells and in the surface mucous gel layer (SMGL) of the normal gastric mucosa or in the mucoid cap adherent to gastric mucosal lesions in Mongolian gerbils. Material and methods. Gastric mucosal lesions were induced in Mongolian gerbils using oral administration of Helicobacter pylori (H. pylori), subcutaneous administration of indomethacin, or oral administration of 30% ethanol. Tissue samples were fixed in Carnoy's solution for preservation of the SMGL, dehydrated, and embedded in paraffin. Histochemical staining for gastric mucins and immunostaining for TFF2 were performed. Results. It was found that surface mucous cell mucin and gland mucous cell mucin were segregated in the SMGL covering the normal gastric mucosa, and the mucin of the mucoid cap covering the mucosal lesions was primarily gland mucous cell mucin. There was a co-localization of TFF2 in gland mucous cell mucin in gland mucous cells, the SMGL, and the mucoid cap. Conclusions. The co-localization of TFF2 in gland mucous cells and in the adherent mucus suggests a physical interaction between TFF2 and gland mucous cell mucin, and the participation of TFF2 trapped in the adherent mucus functions in mucosal defense, healing, and repair.