Search

The roles of cyclooxygenase-2 (COX-2) in the development of gastric cancer are unknown. We investigated the effects of nonsteroidal antiinflammatory drugs (NSAIDs), which are specific and nonspecific inhibitors of COX-2, on proliferation of the gastric cancer cell lines KATOIII, MKN28, and MKN45. The protein level of COX-2 was examined in these cell lines by Western analysis, and mRNA levels of COX-1/2 by Northern analysis. These cell lines expressed comparable levels of COX-1 mRNA. However, mRNA and protein expression of COX-2 in these cell lines was different. MKN45 expressed higher levels of COX-2 mRNA and protein than KATOIII and MKN28. We also examined the effects of NS-398 and indomethacin, specific and nonspecific inhibitors of COX-2, on the increase in cell number and [3H]thymidine uptake of these cell lines. NS-398 and indomethacin suppressed proliferation of MKN45 cells that overexpressed COX-2, although they exerted minimal effects on proliferation of KATOIII and MKN28, which expressed lower levels of COX-2. These results are consistent with the hypothesis that COX-2 is expressed in certain groups of gastric cancers and is related to their cell proliferation. It was proposed that COX-2 plays an important role in development of gastric cancer cells. Furthermore, NSAIDs may exert antiproliferative activity against gastric adenocarcinomas that overexpress COX-2.

Objective: Gastric microcirculatory disturbances are involved in the pathogenesis of stress ulcers; however, vasomodulators causing this process are not fully understood. This study was conducted to investigate the role of endothelin 1 (ET-1), a potent vasoconstrictive peptide, in stress ulcers in critically ill patients., Methods: Using sandwich enzyme immunoassay, we measured ET-1 content in plasma and the gastric mucosa of 16 critically ill patients with traumatic head injury on admission and of 11 healthy subjects. Gastric mucosal samples were obtained endoscopically. When gastric drainage contained occult blood, endoscopic examination was performed again, and ET-1 concentrations in injured and adjacent normal mucosa were compared., Results: Plasma and mucosal ET-1 concentrations were significantly higher in critically ill patients on admission (6.1 +/- 0.6 pg/ml and 13.8 +/- 1.6 ng/g, respectively) compared with values in control subjects (2.7 +/- 0.4 pg/ml and 8.2 +/- 0.5 ng/g, respectively) (p < 0.01). The mucosal ET-1 concentration tended to be elevated in patients who had experienced hypoxia compared with those who had not (p = 0.07). In five patients who were again examined endoscopically, the ET-1 concentration in the injured mucosa was significantly higher than that in adjacent mucosa (19.2 +/- 3.2 and 10.1 +/- 1.6 ng/g, respectively; p < 0.05)., Conclusions: These results suggest that endogenous ET-1 plays an important role in the local pathogenesis of stress ulcers, especially those caused by hypoxia.

Recent epidemiologic studies have shown a 40-50% reduction in mortality from colorectal cancer in individuals who take nonsteroidal antiinflammatory drugs on a regular basis compared with those not taking these agents. One property shared by all of these drugs is their ability to inhibit cyclooxygenase (COX), a key enzyme in the conversion of arachidonic acid to prostaglandins. Two isoforms of COX have been characterized, COX-1 and COX-2. COX-2 is expressed at high levels in intestinal tumors in humans and rodents. Human colon cancer cells (Caco-2) were permanently transfected with a COX-2 expression vector or the identical vector lacking the COX-2 insert. The Caco-2 cells, which constitutively expressed COX-2, acquired increased invasiveness compared with the parental Caco-2 cells or the vector transfected control cells. Biochemical changes associated with this phenotypic change included activation of metalloproteinase-2 and increased RNA levels for the membrane-type metalloproteinase. Increased invasiveness and prostaglandin production were reversed by treatment with sulindac sulfide, a known COX inhibitor. These studies demonstrate that constitutive expression of COX-2 can lead to phenotypic changes that alter the metastatic potential of colorectal cancer cells.

Rat intestinal epithelial cells (RIE-1) permanently transfected with the prostaglandin endoperoxide synthase 2 (also referred to as cyclooxygenase-2; COX-2) gene exhibit decreased cyclin D1 levels, decreased cdk4-associated kinase activity, and delayed G1 cell cycle progression, which represents a phenotype similar to that which follows transforming growth factor beta (TGF-beta) treatment. In the current study, we have found that addition of TGF-beta 1 to the parental RIE-1 cells (designated RIE-P) caused a rapid induction of COX-2 mRNA and protein. COX-2 protein levels progressively increased and reached peak levels 6 h after TGF-beta 1 addition. Cyclin D1 was decreased by 74% at 6 h and was undetectable 24 h after addition of TGF-beta 1. In RIE cells transfected with the COX-2 antisense expression vector (RIE-AS cells), TGF-beta 1 induction of COX-2 protein was reduced greater than 90%. Addition of TGF-beta 1 did not reduce the abundant cyclin D1 protein expression in the RIE-AS cells, unlike the effect in RIE-P cells. TGF-beta 1 treatment reduced peak [3H]thymidine incorporation by 60% and delayed G1/S-phase transition by at least 4 h in the RIE-P cells. In contrast, S-phase entry occurred at 16 h in RIE-AS cells and was not altered by TGF-beta 1 treatment. Restoration of cyclin D1 expression by transfection of the cyclin D1 cDNA under transcriptional control of the cytomegalovirus promoter/enhancer in the COX-2-overexpressing (RIE-S) cells decreased the time required for S-phase entry by at least 4 h and increased the peak level of [3H]thymidine incorporation. Taken together, the results demonstrate that TGF-beta 1 strongly induces COX-2 at both the mRNA and protein levels and suggest that this induction of COX-2 is involved in the down-regulation of cyclin D1 and inhibition of cell growth caused by TGF-beta 1 in rat intestinal epithelial cells.

This article consists of three independent studies regarding Helicobacter pylori-related gastric carcinogenesis. Ammonia, a Helicobacter product, promoted chemically induced gastric carcinogenesis in animals. Moreover, an extract of Helicobacter stimulated inflammatory production of nitric oxide (NO), a potent mutagen that causes G:C-->A:T transition. Meta-analysis of recent studies demonstrated that G:C-->A:T transition is one of the most common mutations in the p53 tumor suppressor gene in early phases of human gastric carcinogenesis. Therefore, bacterial factors such as ammonia and host factors, including inflammatory NO production, might play important roles in H. pylori-induced gastric carcinogenesis.

This study examined the mRNA level of cyclooxygenase-2 (cox-2) in a rat gastric mucosal cell line after growth stimulation in vitro and in rat gastric mucosa before and after acid-induced injury in vivo. RGMI cells were stimulated with fetal calf serum in the in vitro study. Thereafter, the cox-2 mRNA level was examined by Northern analysis. Effects of NS-398, a specific inhibitor of cox-2, and indomethacin on prostaglandin production and cell proliferation were examined in RGM1 cells. In the in vivo study, rats were given 1 ml of 0.6 N hydrochloric acid into the stomach. The level of cox-2 mRNA was examined in rat gastric mucosa after acid administration. Cox-2 mRNA increased 20-60 min after growth stimulation in RGM1 cells. Both NS-398 and indomethacin suppressed prostaglandin production and cell proliferation after growth stimulation. Expression of cox-2 mRNA was observed 40 and 60 min after administration of 0.6 N HCl. Gastric lesions developed within 60 min after HCl administration and healed significantly within 48 h. The present study shows the expression of cox-2 in gastric epithelial cells in vitro and in gastric mucosa after injury in vivo. The results also suggest that cox-2 is involved in de novo synthesis of prostaglandins and cell proliferation in gastric epithelium.

This study examined whether an extract of Helicobacter pylori had the ability to stimulate an inflammatory synthesis of nitric oxide, a mutagen and precursor of nitrosocompounds. Macrophages and neutrophils were prepared from rat and incubated with the Helicobacter pylori extract. L-Arginine-dependent nitric oxide production in these cells was significantly stimulated by the co-incubation with the Helicobacter pylori extract. This ability of the extract was strongly attenuated by protease digestion or heating. These results indicate that Helicobacter pylori induces production of nitric oxide and participates in development of gastritis and gastric carcinogenesis.

Colorectal cancer is the second leading cause of death from cancer in the United States. Continuous use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) has been shown to reduce the risk of colorectal cancer in humans by 40-50%. Patients with familial adenomatous polyposis who take NSAIDs, such as sulindac, undergo a regression of intestinal adenomas. Rodents exposed to carcinogens that cause colon cancer have a 50-60% reduction in the size and number of colonic tumors when treated continuously with NSAIDs. One common target for these drugs is prostaglandin endoperoxide synthase, also referred to as cyclooxygenase (COX). We and others have shown recently that COX-2 levels are increased dramatically in 85-90% of human colorectal adenocarcinomas and in 40-50% of colonic adenomas. We prepared intestinal epithelial cells that express the COX-2 gene permanently and found that they have altered adhesion properties and resist undergoing apoptosis. We report here that these cells also have a 3-fold increase in the duration of G1, lower levels of cyclin D1 protein, and a marked decrease in retinoblastoma kinase activity associated with cyclin-dependent kinase 4. The delay in G1 transit may relate to the resistance of these cells to undergo programmed cell death, which could affect their tumorigenic potential.

Prostaglandin endoperoxide synthase 2, also referred to as cyclooxygenase 2 (COX-2), is a key enzyme in the conversion of arachidonic acid to prostaglandins and other eicosanoids. Rat intestinal epithelial (RIE) cells were permanently transfected with a COX-2 expression vector oriented in the sense (RIE-S) or antisense (RIE-AS) direction. The RIE-S cells expressed elevated COX-2 protein levels and demonstrated increased adhesion to extracellular matrix (ECM) proteins. E-cadherin was undetectable in RIE-S cells, but was elevated in parental RIE (RIE-P) and RIE-AS cells. RIE-S cells were resistant to butyrate-induced apoptosis, had elevated BCL2 protein expression, and reduced transforming growth factor beta 2 receptor levels. The phenotypic changes involving both increased adhesion to ECM and inhibition of apoptosis were reversed by sulindac sulfide (a COX inhibitor). These studies demonstrate that overexpression of COX-2 leads to phenotypic changes in intestinal epithelial cells that could enhance their tumorigenic potential.

Background and Study Aims: This report describes the use of an infrared electronic endoscope for the assessment of gastric mucosal and submucosal hemodynamics in ulcer scars., Methods: The experimental ulcer scars were induced by acetic acid injection in five anesthetized dogs. Indices of mucosal hemoglobin content (IHb) and its oxygenation (ISO2) were calculated from reflectance spectra of the mucosa at 569, 577, 586, and 650 nm, which were obtained through an optic probe. The gastric submucosal vascular diameter was assessed by comparison with a reference wire under infrared endoscopic observation., Results: The index of mucosal hemoglobin content measured by reflectance spectrophotometry was significantly higher at the ulcer scars than in the intact mucosa before the ulcer induction. Intraluminal administration of 0.2 N hydrochloric acid lowered IHb and ISO2 only at the ulcer scars. The diameters of the gastric submucosal veins beneath the ulcer scars decreased markedly after the acid administration., Conclusion: The results suggest abnormal responses of gastric mucosal and submucosal circulation at ulcer scars to intraluminal acid. Infrared electronic endoscopy is therefore a useful tool for the simultaneous analysis of mucosal and submucosal circulation in the stomach.

Hepatocyte growth factor (HGF) stimulates the growth of hepatocytes and other epithelial cells. A gene for the HGF receptor, c-met, is detected in the intestinal tract and the liver, as well as in gastric carcinoma cells. However, the role of HGF in the regeneration of the normal gastric mucosa is not known. The purpose of the present study was to elucidate the effects of HGF on the morphogenesis of cultured gastric mucosal cells and to evaluate the role of HGF and c-met in the healing process in rat gastric mucosa. The cultured gastric mucosal cells developed a branching morphology in a collagen matrix supplemented with HGF or fetal calf serum. They did not form this morphology on a plastic dish or in the collagen without HGF or the serum. In an in vivo study, total RNA was extracted from rat gastric mucosa 6, 24, 48, and 96 hr after the exposure to a solution of 0.6 M HCl. HGF messenger RNA was not detected, but c-met was expressed in the mucosa. The increased expression of c-met was followed by healing of the mucosal injury. These results indicate that HGF plays important roles in the morphogenesis of gastric mucosal cells and that the HGF receptor gene participates in the healing process of gastric mucosa.

Colonic mucosal hemodynamics were investigated at the rectosigmoidal region of the colon in 46 patients with ulcerative colitis and in 18 normal subjects by organ reflectance spectrophotometry under colonoscopy. The value for the index of mucosal hemoglobin concentration (IHb) was significantly higher, and value for the index of mucosal hemoglobin oxygen saturation (ISO2) was significantly lower in patients with active ulcerative colitis than values in the normal controls or in patients with inactive ulcerative colitis. The results indicate mucosal congestion and hypoxemia in patients with active ulcerative colitis. The changes in IHb and ISO2 correlated well with the severity of ulcerative colitis scored by endoscopic findings and with the number of infiltrating inflammatory cells in the mucosa analyzed histologically in biopsy samples. In conclusion, the colonic mucosal microcirculation in patients with active ulcerative colitis was disturbed and showed congestion and hypoxemia. The analysis of hemodynamic changes may be helpful for assessing the activity of ulcerative colitis.

Although an association is suggested between gastric cancer and prior infection with Helicobacter pylori (HP), the role of HP in gastric carcinogenesis remains obscure. HP has potent urease activity and produces ammonia, a factor causing HP-related gastroduodenal mucosal lesions. In this study, rats were examined in an effort to determine effects of ammonia on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). After pretreatment with MNNG (83 mg/l) for 24 weeks, a solution of either 0.01% ammonia or plain tap water was administered to the animals as drinking water for an additional 24 weeks. The administration of the 0.01% ammonia solution significantly increased the incidence and number of cancers in the glandular stomach. The numbers of cases in which these cancers penetrated the muscle layer or deeper and of low-grade differentiated adenocarcinomas were significantly higher in rats receiving the ammonia solution. Continuing administration of ammonia accelerated cell proliferation in the gastric mucosa, but had no effect on the serum gastrin level. Therefore, gastric ammonia, which stimulates mucosal cell proliferation, appears to be an important promoter in carcinogenesis in rats and possibly in the HP-related gastric carcinogenesis in humans.

Background/aims: Endothelium-derived relaxing factor regulates vascular tone via vasodilation. The relative contribution of endogenous nitric oxide to the pathophysiology of ethanol-induced gastric mucosal microcirculatory disturbances was investigated in anesthetized rats., Methods: Macroscopic and microscopic gastric mucosal damage and gastric mucosal hemodynamics including blood flow and hemoglobin oxygen saturation (ISO2) were assessed by pretreatment with a specific NO synthase inhibitor, N omega-nitro-L-arginine (L-NNA), before and after intragastric administration of ethanol., Results: Pretreatment with L-NNA significantly increased macroscopic (7.7-fold) and microscopic damage caused by 30% ethanol. Concurrent administration of L-arginine, but not D-arginine, significantly reduced the increase in mucosal damage. Similar results were obtained with 60% ethanol. Pretreatment with L-NNA decreased both mucosal blood flow and ISO2 in the basal period and enhanced decreases in both mucosal blood flow (2.7-fold) and ISO2 (4.3-fold) induced by 30% ethanol compared with controls. Concurrent administration of L-arginine, but not D-arginine, significantly inhibited the effect of L-NNA on blood flow and ISO2 in the basal period as well as after intragastric administration of 30% ethanol., Conclusions: Endogenous NO modulates ethanol-induced gastric mucosal injury through the regulation of gastric mucosal microcirculation.

In this study, an electronic endoscope was applied for observation of gastric submucosal vessels, with infrared illumination, in anesthetized dogs. An in-vivo spectrophotometry showed that infrared light at 620-820 nm penetrates the abdominal and gastric wall. During the endoscopy performed in dogs, the infrared radiation penetrated the abdominal wall and gastric wall from the outside, and was detected by the endoscope's charge-coupled device. A television monitor displayed a network of gastric vasculature, which was identified as veins in the gastric wall by injecting saline or indocyanine green into the vein. Using this system, it was possible to measure venous diameters of more than 0.2 mm by comparison with a reference wire. The diameter obtained by the image analysis correlated lineally to that of a vascular template prepared from the same stomach. Thus, it may become possible to assess gastric submucosal hemodynamics using infrared endoscopy, a new application in electronic endoscopy.

Growth factors have been shown to play a role in intestinal epithelial growth regulation and transformation. Utilizing standard differential cloning techniques, we have isolated a growth factor-inducible gene (RS-2) from rat intestinal epithelial cells that has approximately 95% homology to the mouse mitogen-inducible cyclooxygenase (COX-2) at the amino acid level. This cDNA hybridizes to a approximately 4.5-kb mRNA from transforming growth factor (TGF)-alpha-stimulated rat intestinal epithelial (RIE-1) cells and is constitutively expressed in vivo in adult rat kidney and brain. Nuclear run-on experiments demonstrate that the increase of RS-2 mRNA after TGF-alpha stimulation is in part due to an increased transcription rate of the gene. The coding region for RS-2 was subcloned into a pCMV-2 expression vector, and the RS-2 protein was expressed in COS-1 cells. Microsomal fractions isolated from the COS-1 cells transfected with the RS-2 expression vector contained cyclooxygenase activity. In addition to the production of prostaglandins, the recombinant RS-2 protein also catalyzed the formation of three other eicosanoid products. In summary, we have cloned a mitogen-inducible cyclooxygenase gene from rat intestinal cells that is induced following growth factor stimulation.

The aim of the present study was to evaluate messenger RNA expression of c-met, a hepatocyte growth factor receptor gene, after gastric mucosal injury in rats. Male Sprague-Dawley rats were fasted for 24 hours, received 0.6 N hydrochloric acid (HCl), and served for polyadenylated RNA extraction from the oxyntic gastric mucosa. The transcripts of rat c-met gene were analyzed by reverse-transcript polymerase chain reaction and Northern blotting. Although it was detected even before the HCl administration, the c-met expression increased 6, 24 and 48 hours after the HCl administration. Thereafter, gastric mucosal injury diminished and the c-met expression declined. Hepatocyte growth factor reportedly plays an important role in gastric cell proliferation. The increased c-met expression indicates that this gene may participate in the healing process of gastric mucosa after injury.

Background/aims: Gastric microcirculatory disturbances are involved in the pathogenesis of stress ulcers; however, vasomodulators regulating this process are not fully understood. This study was conducted to investigate the role of endothelin 1 (ET-1) in hemorrhagic shock-induced gastric mucosal damage in rats., Methods: ET-1 contents in plasma and gastric mucosa were measured and gastric mucosal damage was evaluated during a control period, 60 minutes of ischemia, 15 minutes of reperfusion, and 30 minutes of postreperfusion. Next, effects of BQ-123, an endothelinA receptor antagonist, on the gastric mucosal damage and hemodynamics were studied., Results: Both plasma and mucosal ET-1 significantly increased after ischemia and reperfusion compared with the control values, but only mucosal ET-1 continued to increase after reperfusion, leading to the development of gastric mucosal damage. BQ-123, administered just before reperfusion, reduced mucosal damage in the postreperfusion period dose-dependently and improved mean gastric mucosal blood flow and mucosal hemoglobin oxygen saturation during the 30-minute postreperfusion period., Conclusions: These results suggest that endogenous ET-1 plays an important role in the pathogenesis of hemorrhage shock-induced gastric mucosal damage through impairment of mucosal microcirculation. Further, endothelinA antagonists may have therapeutic benefits for shock-induced gastric mucosal damage.

The major objective of this study was to elucidate the role of endogenous endothelin (ET)-1, a potent vasoconstrictor peptide, in the pathogenesis of ethanol (EtOH)-induced gastric mucosal injury. Two series of experiments were performed in anesthetized rats. First, we examined the time course of relationships among changes in ET-1 concentrations in gastric mucosal and portal plasma, gastric mucosal hemodynamics, and mucosal damage produced by EtOH. Intragastric EtOH stimulated release of endogenous ET-1 in gastric mucosal tissue. Plasma ET-1 concentrations in the portal vein also increased after intragastric EtOH administration. ET-1 concentrations in gastric mucosal tissue and portal plasma increased significantly before gastric mucosal hemorrhagic damage occurred. Moreover, 30 min after EtOH administration there were significant correlations between gastric mucosal ET-1 concentrations and both area of gastric hemorrhagic damage as well as concentration of EtOH administered intragastrically. After intragastric EtOH administration, increase in gastric mucosal hemoglobin concentration and decrease in gastric mucosal hemoglobin oxygen saturation, estimated using reflectance spectrophotometry, occurred within 2.5 min and continued throughout the experiments. The time course of microcirculatory changes correlated closely with increases in gastric mucosal ET-1 and portal plasma ET-1 concentrations after intragastric EtOH administration. Gastric microcirculatory disturbances induced by EtOH were associated with significant decreases in gastric mucosal ATP content. Second, we examined whether pretreatment with anti-ET-1 antibody protected against EtOH-induced mucosal injury by improving mucosal microcirculation. Pretreatment with anti-ET-1 antibody microscopically and macroscopically reduced gastric mucosal hemorrhagic damage induced by EtOH and significantly reduced EtOH-induced gastric microcirculatory disturbances and decreases in gastric mucosal ATP.(ABSTRACT TRUNCATED AT 250 WORDS)

Twelve subjects were examined using both the reflecting type of infrared electronic endoscopy and the transmission method to visualize submucosal gastric architecture. Under transmission infrared illumination, submucosal structures were more clearly observed than by using the reflecting type. Using the transmission method, only the anterior wall of the antrum could be fully visualized, although the anterior wall of the lower corpus was recognized in only 33% of the cases. Furthermore, the upper or middle corpus and the entire posterior wall were not properly recognized using transmission illumination. The entire gastric circumference was visualized with the reflecting type illumination. Both types of infrared illumination of the gastric wall can be used complementarily for visualizing submucosal gastric architecture.

Background: Helicobacter pylori produces ammonia in the stomach from urea. The present study was undertaken to clarify whether ammonia has an etiological role in H. pylori-associated gastric mucosal atrophy., Methods: Ammonia at 0.01% was administered as drinking water for 8 weeks and mucosal cell migration rate and cell proliferation were investigated in rat stomach., Results: Long-term administration of 0.01% ammonia for 4-8 weeks decreased mucosal thickness in the antrum but not in the body. Acceleration of cell migration preceded the occurrence of mucosal atrophy. Labeling indices in both antral and body mucosa significantly increased in all ammonia-treated groups, compared with those of the control group. In the antrum, the proliferative zone was significantly enlarged as mucosal atrophy developed, whereas, in body mucosa, enlargement of the proliferative zone occurred despite the absence of mucosal atrophy., Conclusion: Ammonia at 0.01% accelerates epithelial migration, especially in the antrum, leading to mucosal atrophy. Acceleration of epithelial proliferation occurs during the development of mucosal atrophy.

Helicobacter pylori (HP) has been shown to possibly be a pathogen of gastric carcinoma. HP has urease activity and produces ammonia in the stomach. In this study, the role of ammonia on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in rats. After 24 weeks pretreatment with MNNG (83 mg/l), 0.01% ammonia or tap water as a drinking water was administered for 24 weeks. The ammonia-treated rats showed a significantly higher incidence of gastric cancer (percent of animals with tumors and number of tumors per rat). Ammonia would thus appear to have an important role in HP-related human gastric carcinogenesis.

An electronic endoscope was modified to assess the imaging of two-dimensional distribution of gastrointestinal mucosal hemoglobin with the aid of a computer and image analyzing system. The band-pass filters ranging from 530-470 nm (G'), and 770-830 nm (IR) replaced ordinary filters in a conventional electronic endoscope (Olympus V-10 or EVIS-200). As the hemoglobin is the most abundant biological pigment in the gastrointestinal mucosa absorbing the green light with little absorption in the infrared region, we used the algorithm of 32 [log2(Vir/Vg)] as a reflection of hemoglobin content in the surface mucosa. The algorithm had a good correlation with the spectrophotometrically measured hemoglobin concentration. The mucosal distribution of hemoglobin was displayed in patients with gastric ulcer. In conclusion, the computer and image analyzing system were successfully applied in an attempt to determine gastric mucosal hemoglobin content and its distribution. The possible applications of computers in endoscopic image analysis are discussed.

The mechanism for Helicobacter pylori-induced gastric mucosal injury remains obscure. H. pylori has high urease activity to produce ammonia from urea in the stomach. In this study, the effects of ammonia on (a) gastric mucosal integrity, (b) gastric mucosal hemodynamics, (c) mucosal cellular viability, (d) mitochondrial respiration, and (e) energy metabolism of gastric mucosal were investigated. Ammonia (pH 10.3) at concentrations of greater than 125 mmol/L caused acute macroscopic gastric mucosal lesions in a dose-dependent manner, whereas glycine-NaOH buffer (pH 10.3) or ammonium chloride (pH 4.5) did not. The decrease in energy charge preceded the occurrence of gastric mucosal lesions, but ammonia caused no change in mucosal hemodynamics. Oxygen consumption of isolated cells and mitochondria of gastric mucosa was inhibited by ammonia dose-dependently. The present results indicate that ammonia impairs mitochondrial and cellular respiration and energy metabolism and that ammonia decreases mucosal cell viability, leading subsequently to mucosal damage.

The influences of intravascular ethanol on gastric mucosal integrity and its relation to gastric circulation were investigated in rats. Ulcer formation of the gastric mucosa correlated with the blood ethanol concentration in the presence of 150 mM HCl in the rat stomach. Furthermore, the gastric mucosal hemoglobin concentration (IHb) and hemoglobin oxygen saturation (ISO2), estimated using organ reflectance spectrophotometry, decreased in a concentration-dependent manner with blood ethanol. In isolated, vascularly perfused rabbit stomach, various concentrations (10-400 mM) of ethanol infused into the celiac artery increased the perfusion pressure and released endothelin-1 (ET-1) from the gastric vasculature in a concentration-dependent manner. Moreover, a significant correlation existed between changes in the perfusion pressure and ET-1 concentration in effluents from the gastric vasculature. Furthermore, anti-ET-1 antibody reduced 100 mM ethanol-induced vasoconstriction in a concentration-dependent manner. The results indicate that intravascular ethanol increases the susceptibility of gastric mucosa to injury induced by intraluminal HCl by causing gastric vasoconstriction mediated by ET-1. Thus intravascular ethanol may play an important role in the mechanism of ethanol-induced gastric mucosal injury.

Although many authors reported that proton pump inhibitor showed mucosal protective activity, the precise mechanism is still unclear. In this study, we investigated the effect of proton pump inhibit on gastric mucosal hemodynamics, using a reflectance spectrophotometry system. The proton pump inhibitors had no effect on the gastric mucosal hemodynamics prior to the state of hemorrhagic shock state. However, during the hemorrhagic shock, proton pump inhibitors significantly inhibited the decrease in tissue oxygenation and significantly reduced ulcer formation. In conclusion, proton pump inhibitors maintained tissue oxygenation resulting in reduction of ulcer formation.

A technique of computerized color display was used to analyze the mucosal blood hemoglobin distribution in patients with gastric ulcers. Using an electronic endoscope, red and green images (Vr and Vg) obtained separately from the electronic endoscopic image were transferred to an image analyzer and a computer. The mucosal hemoglobin content was calculated at each pixel of the image using the formula: index of hemoglobin content = 32[log2(Vr/Vg)]. Forty endoscopy examinations were performed in 15 patients with small ulcers (less than or equal to 1 cm) in the gastric angle and 5 normal subjects. The index of hemoglobin content ranged from 24 to 40 in the normal subjects. The index for the area around an active ulcer was mostly below 33. In cases of ulcers in the healing stage it increased to more than 40. The index was still above 40 in ulcer scars in the S1 stage, but within normal range in most of the mucosa in the S2 stage. Thus, the mucosal blood hemoglobin distribution can be assessed by computerized color analysis in patients with gastric ulcers at various stages.

The mucosal blood volume in 20 to 24 different regions of stomach was estimated by reflectance spectrophotometry during endoscopy, and an image showing mucosal blood distribution was made by two-dimensional computer color graphics with the aid of a personal computer. In 55 normal controls, the estimated mucosal blood volume (EMBV) was greater in the corpus mucosa than in the antral mucosa, and less in the lesser curvature than in the greater curvature. The volume in the anterior and posterior walls was almost the same. In 15 patients with active gastric ulcers in the angular region, the EMBV was decreased in all regions in the stomach. In 37 patients with healing ulcers, the EMBV increased, resuming the same levels as in normal controls. However, the EMBV around the ulcer increased remarkably at this stage. In 35 patients with ulcers in the scarring stage, the distribution of the EMBV was similar to that in the normal controls. These hemodynamic changes were shown clearly in a color display with the aid of a personal computer. This method could offer new possibilities in endoscopic research.

Many investigators have reported a decrease in mucosal blood flow resulting in impairment of gastric mucosal energy metabolism in animal experiments. Recently, endoscopic studies using reflectance spectrophotometry and laser Doppler flowmetry have indicated that gastric mucosal blood flow in humans decreases with age. However, changes in energy metabolism in human gastric mucosa with age remains obscure. In this study, we measured adenine nucleotides in biopsy samples from human gastric mucosa, using high-performance liquid chromatography, and investigated changes in energy metabolism with age in subjects proven normal endoscopically. Energy charge (EC = (ATP + 1/2 ADP)/ATP + ADP + AMP) in the gastric antral and body mucosa showed decrease with age. When the subjects were divided into two groups, less than and more than 65 years old, the EC level was significantly lower in the latter than the former in both antral and body mucosa (0.65 +/- 0.06 versus 0.74 +/- 0.03 in the antrum, 0.73 +/- 0.04 versus 0.79 +/- 0.04 in the body) and significantly less in the antral mucosa than in body mucosa in both groups. The adenosine triphosphate (ATP) level in the older group showed a significant decrease (6.48 +/- 1.14 versus 9.63 +/- 1.92 in the antrum, 8.59 +/- 1.64 versus 10.60 +/- 2.13 in the body) compared with those less than 65 years old. In the antral mucosa of the older group the adenosine diphosphate (ADP) level was also significantly lower than that in the group less than 65. In conclusion, in the elderly, the energy metabolism in human gastric mucosa is impaired, and this may weaken their defensive mechanism.

The effects of ethanol on gastric vasculature in isolated vascularly perfused rabbit stomach was investigated. The isolated stomach was perfused with Krebs-Henseleit solution containing 3% dextran bubbled with 95% O2 and 5% CO2 at a rate of 12 ml/min. After mixture and perfusion of 10 mM to 400 mM of ethanol, perfusion pressure and endothelin-1 concentration in effluent from gastric vasculature were measured. Perfusion pressure and endothelin-1 concentration in effluent increased in a dose-dependent manner with increasing ethanol concentrations. In conclusion, the data suggest that ethanol may stimulate the release of endothelin from gastric vasculature and may cause gastric ischemia due to vasoconstriction resulting in acute gastric mucosal injury.

The present series of studies were performed to test the hypothesis that ethanol in the blood may play a role in the pathogenesis of gastric mucosal injury. Another hypothesis to be examined was that endothelin may be involved in ethanol-induced gastric mucosal injury. Elevated levels of blood ethanol induced by intraperitoneal infusion of ethanol increased vulnerability of the stomach to hydrochloric acid in a dose-dependent manner in rats. This may be due to impaired gastric mucosal hemodynamics and oxygenation as demonstrated by the results obtained by organ reflectance spectrophotometry (decreases in indices of mucosal hemoglobin contents and hemoglobin oxygen saturation). Ethanol infusion caused a dose-dependent increase in gastric vascular resistance in perfused rabbit stomach, which was accompanied by an increased production of endothelin-1. The results suggest that endothelin may be involved in the pathogenesis of ethanol-induced gastric mucosal injury.

Although acute gastric mucosal lesions (AGMLs) develop after the mucosal ischemia and reperfusion, precise intracellular mechanism for the development of AGMLs remains unclear. In the present paper, we investigated intracellular calcium level, lipid peroxidation, and gastric mucosal lesion in rat hemorrhagic shock model. We estimated intracellular calcium by measuring phosphorylase a activity in the gastric mucosa. The mucosal phosphorylase a increased during hemorrhagic shock, while it returned to be normal after the reinfusion of shed blood. Although mucosal lipid peroxide and area of AGMLs did not increase significantly during hemorrhagic shock, they increased significantly after the reinfusion. Diltiazem, a calcium antagonist, prohibited both of the increase in mucosal phosphorylase a activity during hemorrhagic shock and the increase in lipid peroxide content and area of AGMLs after the reinfusion of the shed blood. Organ reflectance spectrophotometry revealed that the gastric corpus suffered mucosal ischemia and hypoxia during the hemorrhagic shock. The are of AGMLs had a good correlation with a level of lipid peroxidation in the gastric mucosa. These results suggest 1) that intracellular free calcium in gastric mucosa increases during the mucosal ischemia; 2) that a calcium antagonist prohibits the increased intracellular free calcium during mucosal ischemia; and 3) that a calcium antagonist prohibits the increased mucosal lipid peroxide and the development of AGMLs after the mucosal reperfusion. Thus it is concluded that the increased intracellular free calcium during ischemia plays a key role in the mucosal tissue injury in the ischemia-reperfusion state.

The prevalence of Helicobacter pylori (HP) in the gastric mucosa of patients with chronic atrophic gastritis has been reported to be significantly higher than in normal mucosa. To clarify the role of HP in the etiology of chronic atrophic gastritis, we assessed the effect of ammonia on the gastric mucosal structure in rats, since HP has a strong urease activity and produces abundant amounts of ammonia. Ammonia administered orally at 0.01% and 0.1% as drinking water for two to four weeks decreased the mucosal thickness and the parietal cell number and oxyntic gland number in a dose- and time-dependent manner. The decrease of mucosal thickness was significantly greater in the antral mucosa than in the body mucosa. The border between the antral and body mucosa shifted toward the cardia, reflecting the decrease in oxyntic gland numbers. Furthermore, intracellular mucin was also decreased in a dose- and time-dependent manner, especially in the antral mucosa. Thus, ammonia chronically administered orally in rats led to changes in gastric mucosal structures and functions. The results suggest that the ammonia produced by HP partly plays an etiologic role in chronic atrophic gastritis.

To elucidate the role of Helicobacter pylori infection in the pathogenesis of gastric ulcer, we investigated the intracellular mucin content by measuring the periodic acid-Schiff-Alcian blue (PAS-AB)-stained substances, by means of computer, in the biopsy sample of gastric mucosa from patients with and without H. pylori infection. In the antral mucosa the intracellular PAS-AB-stained mucin content was significantly smaller in patients with infection than in patients without infection, whereas in the oxyntic gland mucosa the intracellular mucin content showed no significant change between patients with and without infection. In an animal study we investigated the effect of ammonia, which might be produced by H. pylori in the presence of urea. The ammonia, administered orally, caused a greater decrease of intracellular PAS-AB-stained mucin content in the gastric antral mucosa than in the body mucosa, in a dose-dependent manner. The results suggested that H. pylori infection had a different effect on the gastric mucosal intracellular PAS-AB-stained mucin and lowered specifically the antral intracellular PAS-AB-stained mucin content, possibly due to generation of ammonia by H. pylori.

DQ-2511, which is a dopamine derivative, is a newly synthesized anti-ulcer drug. Pretreatment with DW-2511 in the hemorrhagic shock-reperfusion model in rats significantly prevented the decreases of gastric mucosal blood volume, mucosal blood oxygenation index and the ulcer formation. The decrease in gastric mucosal blood oxygenation index in hemorrhagic shock state has a linear correlation with the size of the mucosal ulcers both in DQ-2511 and control groups. The results suggested that DQ-2511 exerts its anti-ulcer activity by improving mucosal hemodynamics in hemorrhagic shock-reperfusion rat model.

While gastric mucosa contains prostaglandins and leukotrienes, the roles of these substances in the gastric mucosal protection and damage are not clarified. Using AA-861, a specific 5-lipoxygenase inhibitor, and indomethacin, a cyclooxygenase inhibitor, we investigated the roles of intrinsic prostaglandins and leukotrienes in the gastric circulatory change and the development of gastric lesion induced by ethanol. Rats were fasted for 48 hours and allowed free access to water. After light ether anesthesia, rats were orally given AA-861 (gift from Takeda Chem. Industry; 2.5, 10, 40 or 640 mg/kg), indomethacin (20 mg/kg), and the both or AA-861 (40 mg/kg) and indomethacin (20 mg/kg). Thirty min after the treatment, 2 ml of ethanol (30, 40, 70, 99.5%) was orally administered. Sixty min later, the rats were killed to measure the area of mucosal lesions. The gastric mucosa was damaged by ethanol (greater than or equal to 40%) in a dose-dependent manner. The treatment with AA-861 prohibited the gastric mucosal damage. However, the treatment with indomethacin did not show a significant influence to the mucosal damage. Combined treatment of AA-861 and indomethacin yielded no significant difference from that of single treatment with AA-861 in acute gastric mucosal ulceration. The mucosal blood flow velocity was monitored by laser doppler velocimetry before and after the ethanol administration in the groups treated with vehicle, AA-861 or indomethacin. The blood flow velocity decreased after the administration of 40% ethanol in the group treated with indomethacin, and in a group treated with vehicle.(ABSTRACT TRUNCATED AT 250 WORDS)

To investigate the role of the intracellular calcium ion in the development of acute gastric mucosal lesions, phosphorylase a activity was measured as an index of the intracellular calcium ion concentration ([Ca2+]i), using Lowry's method, in the rat ischemia-reperfusion model. [Ca2+]i increased significantly at the end of the ischemic state without acute mucosal lesions (AGML). After reinfusion, [Ca2+]i showed a slight increase and AGML developed. Continual intravenous infusion of the calcium channel blocker, diltiazem (1 mg/kg/hr), inhibited the increase in [Ca2+]i in the ischemic state and reduced the development of AGML after reinfusion. These results suggest that the increase in [Ca2+]i in the ischemic state plays an important role in the development of AGML.

The acute effect of cigarette smoking on the gastric mucosal blood volume index and the oxygen saturation of hemoglobin (SO2) in the gastric mucosa was investigated in 12 young male volunteers using reflectance spectrophotometry during endoscopy. Six of these volunteers were habitual smokers who had smoked more than 20 cigarettes a day for more than five years. The others were non-habitual smokers who smoked less than 20 cigarettes a year. The indices of mucosal blood volume and the mucosal blood SO2 level were calculated from the spectra obtained at the lesser curvature of the lower corpus of the stomach before and after cigarette smoking. The indices of mucosal blood volume and mucosal blood SO2 decreased significantly after one to three puffs of cigarette smoking in all subjects as compared to the value before smoking, and the degree of decrease in these parameters was significantly greater in the non-habitual smokers than in the habitual smokers. These results suggest that only one to three puffs of cigarette smoking causes a decrease in the mucosal blood volume and the mucosal blood SO2 which might be related to weakening of mucosal defensive factors.