Digestion

Yu, Hidenori; Sato, Eisuke F.; Minamiyama, Yukiko; Arakawa, Tetsuo; Kobayashi, Kenzo; Inoue, Masayasu

doi: 10.1159/000201461pmid: 9324158

Although nitric oxide (NO) has been known to play important roles in various biological events, the pathophysiological role of NO in the stomach remains to be elucidated. Since endotoxin induces NO synthase (NOS) in various tissues, the effect of lipopolysaccharide (LPS) on the stomach was studied in rats which were given water-immersion-restraint (WIR) stress. WIR treatment significantly increased the vascular permeability of gastric mucosa and induced mucosal injury. When LPS was injected intravenously to the rat, inducible-type NOS (iNOS) markedly increased in the gastric smooth muscular layer without affecting levels of brain-type isozyme (bNOS). LPS also increased gastric mucosal blood flow but suppressed the secretion of gastric acid. N^G-(1-iminoethyl)-L-ornithine (NIO), a potent inhibitor of NOS, completely inhibited the LPS-induced increase in mucosal blood flow without affecting the acid secretion in control and LPS-treated rats. LPS markedly suppressed the WIR-induced mucosal injury by some NIO-inhibitable mechanism. These findings suggested that NO derived from gastric iNOS might play important roles in the suppression of stress-induced mucosal injury of the stomach.

Brzozowski, Tomasz; Konturek, Stanislaw J.; Sliwowski, Zbigniew; Pajdo, Robert; Drozdowicz, Danuta; Stachura, Jerzy

doi: 10.1159/000201462pmid: 9324159

The central and peripheral adrenergic systems are involved in the regulation of gastric secretion but little is known about the role of α- and β-adrenoceptors in gastroprotection. In this study, acute gastric lesions were produced by an intragastric (i.g.) application of 100% ethanol and gastric blood flow (GBF) was determined by H₂-gas clearance technique in rats with or without i.g. or intraperitoneal (i.p.) administration of α- or β-adrenoceptor agonists or antagonists. Phenylephrine, α₁-adrenergic agonist, and clonidine, α₂-agonist, significantly augmented the ethanol-induced lesions while decreasing the GBF and these effects were reversed by the blockade of α₁-adrenoceptors with prazosin and α₂-adrenoceptors with yohimbine. In contrast, isoproterenol (ISO) (0.01-10 mg/kg i.g.), β-adrenoceptor agonist, reduced dose-dependently ethanol-induced mucosal injury and this effect was accompanied by an elevation of the GBF similarly as after epidermal growth factor (EGF) (100 μg/kg·h s.c.) or after classic protective agent, 16,16-dimethyl-PGE₂ (PGE₂) (10 μg/kg i.g.). The pretreatment with β-antagonist, propranolol, diminished the protective and hyperemic effects of ISO and EGF but failed to affect those induced by PGE₂. Suppression of nitric oxide (NO) synthase activity by L-NAME or sensory denervation with capsaicin attenuated significantly the ISO- and EGF-induced gastroprotection and elevation of GBF, whereas the inhibition of PG biosynthesis by indomethacin remained without any significant effect. Adrenal medullectomy or chemical sympathectomy by 6-hydroxydopamine by itself failed to influence significantly the ethanol-induced damage but completely abolished the protective and hyperemic effects of EGF being without any influence on those induced by PGE₂. ISO combined with EGF, restored the protective and hyperemic effects of this peptide in medullectomized rats. We conclude that (1) local activation of β-adrenoceptors by ISO affords protection and elevation of GBF, both these effects being mediated by arginine-NO pathway and sensory nerves and (2) sympathetic system and adrenal medulla contribute to the protective and hyperemic activity of EGF.

Hirose, Y.; Goto, H.; Arisawa, T.; Hase, S.; Niwa, Y.; Hayakawa, T.; Asai, J.; Tsukamoto, Y.

doi: 10.1159/000201463pmid: 9324160

Objective: The authors reported that the repair of submucosal tissue is important in ulcer healing. The kinetics of fibroblasts have not been well known in gastric ulcer healing. The effect of subcutaneous administration of indomethacin (1 mg/kg) to submucosal tissue was also examined. Method: Immunohistological staining was done using the antibodies for the proliferating cell nuclear antigen prolyl 4-hydroxylase and α-smooth muscle actin in acetic acid induced gastric ulcers in rats. The terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate-biotin nick end labeling method was also employed. Results: The granulation tissue consisted predominantly of lymphocytes in indomethacin-treated rats. In the control group, proliferative cell nuclear antigen positive cells were at their peak 5 days after ulcer formation (day 5). Prolyl 4-hydroxylase positive fibroblasts were maximal on day 10. α-Smooth muscle actin positive myofibroblasts were few on day 5 and increased on day 15. In terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate-biotin nick end labeling, positive cells were sporadically seen on days 20 and 30. In indomethacin-administered rats, the fibroblasts proliferated weakly. The numbers of prolyl 4-hydroxylase and α-smooth muscle actin positive spindle-shaped cells were fewer and their appearance delayed. Nick end labeling positive cells were few before day 30 and sporadically observed on days 50 and 80. Conclusion: The results indicate that fibroblasts differentiated into several phenotypes and finally underwent apoptosis.

Nishida, Keiji; Ohta, Yoshiji; Kobayashi, Takashi; Ishiguro, Isao

doi: 10.1159/000201464pmid: 9324161

In rats subjected to water immersion restraint (WIR) stress for 1, 3, and 6 h, gastric mucosal lesions developed time-dependently with an increase in lipid peroxide (LPO) levels and a decrease in nonprotein sulfhydryl levels in the gastric mucosa. The gastric mucosal xanthine oxidase (XO) activity significantly increased with the conversion of xanthine dehydrogenase (XD) to XO at 6 h of WIR (3.2-fold that of the control group without WIR). A significant increase in myeloperoxidase (MPO) activity, an index of neutrophil infiltration, occurred in the gastric mucosa at 3 and 6 h of the WIR (2.2- and 3.3-fold that of the control group without WIR, respectively). In contrast, superoxide dismutase, catalase, and glutathione peroxidase activities in the gastric mucosa did not change during the WIR period. Pretreatment with either allopurinol (AP), an inhibitor of XO, or soybean trypsin inhibitor (STI), a serine protease inhibitor, attenuated the lesion development at 6 h of WIR, but not at 3 h. In the gastric mucosa of rats pretreated with AP, enhancements of LPO formation, sulfhydryl oxidation, and XO activity found at 6 h of WIR were prevented with inhibition of XD plus XO activity, while in the gastric mucosa of rats pretreated with STI, these enhancements were prevented with inhibition of the conversion of XD to XO. In the gastric mucosa of rats pretreated with anti-polymorphonuclear leukocyte antiserum, the lesion development and enhanced LPO formation and sulfhydryl oxidation found at 3 and 6 h of WIR were prevented with a decrease in increased MPO activity. These results indicate that in the gastric mucosa of rats with WIR stress, the progression of lesions is mainly related to enhanced LPO formation and sulfhydryl oxidation which depend on an increased generation of oxygen free radicals via the xanthine-XO system and neutrophils rather than the change in the oxygen free radical-scavenging activity of antioxidant enzymes. The present results also suggest that increased gastric mucosal LPO formation and sulfhydryl oxidation found at 3 h of WIR could be mainly due to neutrophil-derived oxygen free radicals, while enhanced gastric mucosal LPO formation and sulfhydryl oxidation found at 6 h of WIR could be due to both neutrophil- and XO-derived oxygen free radicals.

Payne, N.A.; Gerber, J.G.

doi: 10.1159/000201465pmid: 9324162

The effects of adenosine and histamine 2 and histamine 3 receptor agonists on the regulation of gastric histamine release were examined in anesthetized mixed-breed dogs. All compounds were infused directly into the gastrosplenic artery to avoid perturbations in systemic hemodynamics, and the gastric histamine release was stimulated with pentagastrin. The histamine concentration in plasma samples was measured utilizing gas chromatography-negative-ion chemical ionization mass spectroscopy. Pentagastrin consistently stimulated gastric histamine release with the peak stimulation occurring at 5 min, while neither 30 nor 100 μM of adenosine altered the effect of pentagastrin on histamine release. In addition, theophylline at 20 μg/ml exhibited no effect on stimulated histamine release. The histamine 2 receptor agonist dimaprit, at 1 and 3 μM, attenuated pentagastrin-stimulated histamine release at the 5-min time period, but the difference was not sustained at later time points (histamine release from 1.4 ± 0.6 to 92 ± 18 ng/min at 5 min with pentagastrin alone; from 1.2 ± 0.5 to 32 ± 11 ng/min with pentagastrin plus 1 μM dimaprit, and from 2.0 ± 1.1 to 32 ± 9 ng/min with pentagastrin plus 3 μM dimaprit), while the H₂ receptor antagonist cimetidine exhibited no effect on pentagastrin-stimulated histamine release. The histamine 3 receptor agonist (R)-α-methyl-histamine attenuated the pentagastrin-stimulated histamine release at the 5-and 10-min time periods only at 1 μM without showing any effect at the higher (3 μM) concentration. Thioperamide, a H₃ receptor antagonist, did not modify pentagastrin-stimulated histamine release. These data demonstrate that adenosine has no modulatory role on gastric histamine release, but histamine via H₂ and H₃ histamine receptors could modulate its own release but only to a modest degree as compared with the potent effect of the paracrine hormone somatostatin.

Dabrowski, Andrzej; Detjen, Katharina M.; Logsdon, Craig D.; Williams, John A.

doi: 10.1159/000201466pmid: 9324163

It was recently found that cholecystokinin (CCK) activates mitogen-activated protein kinases (MAPK) in isolated rat pancreatic acini. The present study evaluates whether one or both types of CCK receptors are capable of MAPK activation in pancreatic AR42J acinar cells as well as CHO cells transfected with CCK-A or CCK-B receptors. CCK significantly increased p44 MAPK and p42 MAPK activities in AR42J cells. Minimal, half-maximal, and maximal responses were observed at 30 and 500 pM and 10 nM, respectively, after CCK-8 stimulation and at 100 pM and 1.5 and 30 nM, respectively, after gastrin stimulation. Glycine-extended gastrin had no effect at 100 nM and a small but significant effect at 1 μM. The CCK-B receptor antagonist L365,260 almost totally blocked MAPK activation in AR42J cells after stimulation with gastrin and glycine-extended gastrin and substantially reduced the activation of both kinases by CCK-8, while the CCK-A receptor antagonist L364J18 was much less effective. The CCK-A-selective agonist A71376, however, was an effective stimulant of MAPK activity. In an alternative approach, stably transfected CHO cells bearing either CCK-A or CCK-B receptors were stimulated with CCK-8. Each receptor induced a time-dependent increase in activity of both MAPKs by five- to sixfold in CCK-A- and CCK-B-bearing cells. In conclusion, both CCK-A and CCK-B receptors activate MAPK in AR42J cells and in transfected CHO cells.

Farghaly, M.; Khoursheed, M.; Dashti, H.; Thulesius, O.

doi: 10.1159/000201467pmid: 9324164

In vitro contractility of human and sheep gallbladders to cholinergic stimulation with carbachol and the effects of indomethacin on abnormal rhythmic activity were studied. Once hundred and thirdy-two gallbladders were obtained at laparoscopic cholecystectomy, 38 from patients with acute and 94 with chronic cholecystitis. In addition, 27 specimens of sheep gallbladders served as controls. Fundal preparations from patients with cholecystitis exhibit hypocontractility: no response in 72% or in the remainder a significantly reduced maximal contraction to carbachol. Regionally graded motor responses favoring propulsion of bile were abnormal in 44% ofthe gallbladders studied with more forceful contractions of the duct compared to the fundus. Abnormal early rhythmic activity (ERA) of fundal preparations was only detected in gallbladders of patients (in 33%) but never in controls. In 80% of these, ERA was blocked or reduced by indomethacin which can be interpreted as evidence for a prostaglandin-mediated inflammatory response. We conclude that gallbladder motility in cholelithiasis secondary to muscarinic stimulation is reduced and regionally graded motor responses favoring bile expulsion are impaired. ERA can be blocked by indomethacin.

Konturek, J.W.; Konturek, S.J.; Pawlik, T.; Domschke, W.

doi: 10.1159/000201468pmid: 9324165

This study was designed to determine the role of nitric oxide in gallbladder (GB) contractions in men. The studies were performed in 10 young healthy male volunteers. GB emptying was examined by ultrasonography under basal conditions and after intravenous infusion of cholecystokinin (CCK8; 12.5 pmol/kg·h) or yolk intake in tests without (saline) and with intravenous infusion of N^G-monomethyl-L-arginine (L-NMMA; 4.0 μmol/kg·h) and/or L-arginine (1 mmol/kg·h). The plasma CCK level was determined by radioimmunoassay. It was found that the basal GB volume was about 27 ± 3 ml, and after CCK8 infusion or yolk meal this volume was reduced within about 30 min by about 93 and 80%, respectively. Pretreatment with L-NMMA caused reduction of the baseline volume by about 15% and significantly augmented the GB emptying induced by CCK8 infusion and yolk intake. L-Arginine alone failed to affect basal or stimulated (CCK or yolk) emptying of the GB, but when combined with L-NMMA, it reversed the enhancement of GB contraction caused by L-NMMA. The basal plasma CCK level was 1.2 ± 0.3 pmol/l and rose to 7.9 ± 2.1 pmol/l with CCK8 infusion and to 4.7 ± 1.8 pmol/l after yolk meal. No significant change in plasma CCK levels was observed in tests with L-NMMA and/or L-arginine. We conclude that under physiological conditions, the GB contractile activity is regulated predominantly by CCK, but endogenous nitric oxide has a tonic relaxing influence on this activity.

Fabbri, Andrea; Bianchi, Giarnpaolo; Brizi, Mara; Zoli, Marco; Marchesini, Giulio

doi: 10.1159/000201469pmid: 9324166

The uncertainty in liver function assessment based on single-sample galactose levels after galactose injection, in comparison to the standard procedure using the galactose elimination capacity (GEC), was assessed in 905 tests performed in a wide range of liver functions. The 45-min galactose levels significantly correlated with GEC, the correlation being better in subjects with a good liver function. In cirrhosis, the prediction using the 60-min galactose value was better than when the 45-min value was used. In the whole series, the 95% confidence interval of GEC predicted by 45-min galactose was as large as ± 1.55 mg•kg^-1•min^-1 as absolute value, corresponding to a range from-41 to +47% of measured GEC. In cirrhosis, the 95% confidence interval was ± 1.42 mg•kg^-1•min^-1 and between -40 and +46% of measured GEC. The 60-min values were more predictive, but in Child class C patients the average error was 0.42 mg•kg^-1•min^-1 (95% confidence interval -0.64 to +1.49, corresponding to -39 to +76% of measured GEC). The uncertainty was maintained within ± 10% of measured values only in 50% of the tests. We conclude that the single-point galactose test introduces a considerable error, mainly in patients with more advanced liver disease, which may bias the decision-making process.

Takashimizu, Ichizen; Ohkusa, Toshifumi; Okayasu, Isao; Sato, Chifumi

doi: 10.1159/000201470pmid: 9324167

To study the effects of percutaneous ethanol injection therapy on livers, we investigated necrotic changes after ethanol injection and fibrotic changes during the repair process in cirrhotic livers in comparison with normal livers. Male rats were treated with oral doses of 3’-methyl-4-dimethylaminoazobenzene and thioacetamide to produce liver cirrhosis. Both control animals and cirrhotic animals were injected with 0.2 ml of absolute ethanol into livers. Histological samples were cut serially, and the maximum areas of necrosis and fibrosis were measured until 28 days after the injection. Although the maximum area of necrosis was not different between cirrhotic livers and control livers, the average fibrotic ratio [(maximum fibrotic area/maximum necrotic area + maximum fibrotic area) × 100] was 64% in control livers (n = 9) and 40% in cirrhotic livers (n = 9; p < 0.05). The fibrotic repair process after ethanol injection seems to be impaired in cirrhotic livers as compared with normal livers.