Gastric secretion

Spirulina supplements: an approach moderating aspirin persuaded histological and ultra-structural alterations in albino rats gastric mucosa

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most used drugs. The pathogenesis of aspirin-induced gastric ulceration includes blocking the activities of the cyclooxygenase enzymes (COX-1 and COX-2) leading to reduced mucus and bicarbonate secretion. Spirulina contains many functional bioactive ingredients with antioxidant and anti-inflammatory activities, including phenolic phytochemicals and phycobiliprotein C-phycocyanin. To investigate the possible gastroprotective role of spirulina against aspirin-induced gastric mucosal insults. Forty adult male albino rats were randomly divided into four experimental groups. Group I (Control) and group II (Spirulina control) were given spirulina for 3 days, group III (Ulcer model) were given single dose of acetyl salicylic acid to induce ulcer and group IV (Treatment) were given spirulina for 3 days after induction of ulcer formation. Animals were sacrificed, stomachs were collected and processed for examination of light and scanning electron microscope histopathological examination. Statistical difference mucosal mucin area percentage among groups was determined and data were analyzed. Histological examination of the H&E-stained and combined Alcian-blue-PAS-stained sections of Group III rats illustrated severe destruction of the mucosal architecture and reduction of the mucin surface area while those examined for group IV illustrated minor affection of the gastric mucosa and mucin protective layer. Oxidant antioxidant markers: Nitric oxide (NO) is elevated, Glutathione (GSH) and superoxide dismutase (SOD) are reduced in aspirin treated group. The use of Spirulina restores the normal balance between the oxidant antioxidant system. Spirulina has a great potential in protecting the gastric mucosa against harmful effect of NSAID.

Physiological insights into electrodiffusive maintenance of gastric mucus through sensitivity analysis and simulations

It is generally accepted that the gastric mucosa and adjacent mucus layer are critical in the maintenance of a pH gradient from stomach lumen to stomach wall, protecting the mucosa from the acidic environment of the lumen and preventing auto-digestion of the epithelial layer. No conclusive study has shown precisely which physical, chemical, and regulatory mechanisms are responsible for maintaining this gradient. However, experimental work and modeling efforts have suggested that concentration dependent ion-exchange at the epithelial wall, together with hydrogen ion/mucus network binding, may produce the enormous pH gradients seen in vivo. As of yet, there has been no exhaustive study of how sensitive these modeling results are with respect to variation in model parameters, nor how sensitive such a regulatory mechanism may be to variation in physical/biological parameters. In this work, we perform sensitivity analysis (using Sobol' Indices) on a previously reported model of gastric pH gradient maintenance. We quantify the sensitivity of mucosal wall pH (as a proxy for epithelial health) to variations in biologically relevant parameters and illustrate how variations in these parameters affects the distribution of the measured pH values. In all parameter regimes, we see that the rate of cation/hydrogen exchange at the epithelial wall is the dominant parameter/effect with regards to variation in mucosal pH. By careful sensitivity analysis, we also investigate two different regimes representing high and low hydrogen secretion with different physiological interpretations. By complementing mechanistic modeling and biological hypotheses testing with parametric sensitivity analysis we are able to conclude which biological processes must be tightly regulated in order to robustly maintain the pH values necessary for healthy function of the stomach.

Carvedilol safeguards against aspirin-induced gastric damage in rats

This study investigated the effect of carvedilol on aspirin-induced gastric damage. Male Wistar rats were divided into three groups. Control rats received the vehicle, while the aspirin group received aspirin (200 mg/kg) orally for 4 days. Rats of aspirin + carvedilol group were administered aspirin along with carvedilol (5 mg/kg; intraperitoneal) for 4 days. Animals were euthanized at the end of the treatment period, and gastric tissues were collected to perform histopathological and mechanistic studies. The results revealed that aspirin administration induced gastric ulcer as there were remarkable histopathological lesions in the form of marked necrosis, inflammation, hemorrhage, edema, and dysplastic changes. Lipid peroxidative markers such as malondialdehyde, 4-hydroxynonenal, and protein carbonyl were significantly elevated in the aspirin group. This was concurrent with a significant amelioration of antioxidants such as reduced glutathione, superoxide dismutase, and catalase. Furthermore, aspirin increased the immunoexpression of cyclooxygenase (COX) 2 and nuclear factor kappa-B (NF-κB). Aspirin induced elevation in the inflammatory cytokines such as tumor necrosis factor-α, interleukin-6, and interleukin-1β. Aspirin enhanced the immunoexpression of inducible nitric oxide synthetase (iNOS) and increased the level of nitrite/nitrate in gastric tissue. On the other hand, carvedilol treatment reversed all these pathological changes. Carvedilol succeeded to enhance antioxidants in gastric tissue, attenuated lipid peroxidative parameters, and suppressed the release of inflammatory mediators. It attenuated the immunoexpression of COX-2, NF-κB, and iNOS. Collectively, carvedilol has a gastro-protective effect that could be attributed to its antioxidative and anti-inflammatory properties, which modulate NF-κB/COX-2/iNOS pathways.

A physics-based model for maintenance of the pH gradient in the gastric mucus layer

It is generally accepted that the gastric mucus layer provides a protective barrier between the lumen and the mucosa, shielding the mucosa from acid and digestive enzymes and preventing autodigestion of the stomach epithelium. However, the precise mechanisms that contribute to this protective function are still up for debate. In particular, it is not clear what physical processes are responsible for transporting hydrogen protons, secreted within the gastric pits, across the mucus layer to the lumen without acidifying the environment adjacent to the epithelium. One hypothesis is that hydrogen may be bound to the mucin polymers themselves as they are convected away from the mucosal surface and eventually degraded in the stomach lumen. It is also not clear what mechanisms prevent hydrogen from diffusing back toward the mucosal surface, thereby lowering the local pH. In this work we investigate a physics-based model of ion transport within the mucosal layer based on a Nernst-Planck-like equation. Analysis of this model shows that the mechanism of transporting protons bound to the mucus gel is capable of reproducing the trans-mucus pH gradients reported in the literature. Furthermore, when coupled with ion exchange at the epithelial surface, our analysis shows that bicarbonate secretion alone is capable of neutralizing the epithelial pH, even in the face of enormous diffusive gradients of hydrogen. Maintenance of the pH gradient is found to be robust to a wide array of perturbations in both physiological and phenomenological model parameters, suggesting a robust physiological control mechanism.NEW & NOTEWORTHY This work combines modeling techniques based on physical principles, as well as novel numerical simulations to test the plausibility of one hypothesized mechanism for proton transport across the gastric mucus layer. Results show that this mechanism is able to maintain the extreme pH gradient seen in in vivo experiments and suggests a highly robust regulation mechanism to maintain this gradient in the face of dynamic lumen composition.

Gastro-protective effect of methanol extract of Vernonia amygdalina (del.) leaf on aspirin-induced gastric ulcer in Wistar rats

This study investigated the protective effects of methanol extract of Vernonia amygdalina leaf (MEVA) on aspirin induced gastric ulcer in rats. Thirty Wistar rats, 150-200 g were divided into six groups as follows: Group 1 (control) rats received 2 mL/kg of propylene glycol for 28 consecutive days. Group 2 (Ulcer Control) received 150 mg/kg/day of aspirin suspended in 3 mL of 1% carboxymethylcellulose in water orally for 3 consecutive days during which the rats were fasted for the induction of ulcer. Group 3 received cimetidine at 100 mg/kg/day orally for 28 consecutive days and thereafter treated as group 2. Groups 4, 5 and 6 received MEVA orally at 200, 300 and 400 mg/kg/day respectively for 28 consecutive days and thereafter were treated with aspirin as group 2. All the animals were sacrifice at the end of the study to determine the gastric pH, gastric acidity, gastric ulcer score, haematological indices, superoxide dismutase (SOD) activity, reduced glutathione (GSH) and Lipid peroxidation (LPO) levels. The result showed that aspirin significantly (p < 0.05) increased gastric ulcer score and index, decreased gastric pH, gastric acidity, SOD activity, GSH level as well as increased LPO level. It induced significant necrosis of the stomach tissue. Administration of MEVA significantly (p < 0.05) increased gastric pH, but decreased gastric acid secretion and reversed alteration of haematological parameters. It also significantly (p < 0.05) increased SOD activity, GSH level and decreased LPO level. The results suggest that Vernonia amygdalina possesses gastro-protective properties against aspirin-induced gastric ulcer.

Changes in small intestinal motility and related hormones by acupuncture stimulation at Zusanli (ST 36) in mice

OBJECTIVES

To clarify the effects of acupuncture stimulation at Zusanli (ST 36) on the hormonal changes.

METHODS

Eight-week-old male C57BL/6 mice received acupuncture stimulation at acupoint ST 36 or Quchi (LI 11) once a day for 3 or 5 days in the acupuncture-stimulated groups, but not received in the normal group (n=6 in each group). On day 3 or 5, animals were given 0.1 mL of charcoal orally with a bulbed steel needle, 30 min after the last acupuncture stimulation. Ten minutes later, mice were anesthetized, and the intestinal transit and the concentrations of vasoactive intestinal peptide (VIP), motilin, ghrelin and gastrin in the serum were measured.

RESULTS

Compared to no acupuncture stimulation, acupuncture stimulation at ST 36 for 5 days increased the intestinal transit and down-regulated the concentration of VIP and up-regulated the concentrations of motilin, ghrelin and gastrin (P<0.05 or 0.01), whereas acupuncture stimulation at LI 11 did not change them signifificantly (P>0.05).

CONCLUSION

Acupuncture stimulation at ST 36 for 5 days enhances the small intestinal motility and regulates the secretion of hormones related to small intestinal motility.

Gastroprotective effect of andrographolide sodium bisulfite against indomethacin-induced gastric ulceration in rats

Andrographolide sodium bisulfite (ASB), a water-soluble sulfonate of andrographolide has been shown to possess anti-inflammatory, antipyretic and analgesic activities. However, there is no report on the gastroprotective effect of ASB against indomethacin-induced gastric ulcer. Here we investigated the possible anti-ulcerogenic potential of ASB and the underlying mechanism against indomethacin-induced gastric ulcer in rats. The ulcer area, histopathological assessment, contents of gastric mucosal glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), malonaldehyde (MDA) and prostaglandin E2 (PGE2) were examined. In addition, cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2) mRNA expression and immunohistochemical evaluation of HSP70, Bcl-2 and Bax proteins were also investigated. Results indicated that ASB pre-treatment significantly reduced the ulcer areas induced by indomethacin compared with the vehicle group. The gastric levels of GSH, CAT and SOD were markedly increased by ASB while the level of MDA was decreased. In addition, ASB pretreatment significantly promoted the gastric PGE2 levels and up-regulated the COX-1 and COX-2 mRNA expression in comparison with the vehicle group. Immunohistochemistry analysis showed obvious up-regulation of HSP70 and Bcl-2 protein expression while suppression of Bax protein in the gastric tissue of ASB-pretreated group. Taken together, these findings indicated that the gastroprotective effect of ASB might be associated with the improvement of antioxidative status, activation of COX-mediated PGE2 synthesis, down-regulation of Bax proteins and up-regulation of Bcl-2 and HSP70 proteins. ASB might have the potential for further development as a promising alternative for antiulcer treatment.

Characterization of gastric and neuronal histaminergic populations using a transgenic mouse model

Histamine is a potent biogenic amine that mediates numerous physiological processes throughout the body, including digestion, sleep, and immunity. It is synthesized by gastric enterochromaffin-like cells, a specific set of hypothalamic neurons, as well as a subset of white blood cells, including mast cells. Much remains to be learned about these varied histamine-producing cell populations. Here, we report the validation of a transgenic mouse line in which Cre recombinase expression has been targeted to cells expressing histidine decarboxylase (HDC), which catalyzes the rate-limiting step in the synthesis of histamine. This was achieved by crossing the HDC-Cre mouse line with Rosa26-tdTomato reporter mice, thus resulting in the expression of the fluorescent Tomato (Tmt) signal in cells containing Cre recombinase activity. As expected, the Tmt signal co-localized with HDC-immunoreactivity within the gastric mucosa and gastric submucosa and also within the tuberomamillary nucleus of the brain. HDC expression within Tmt-positive gastric cells was further confirmed by quantitative PCR analysis of mRNA isolated from highly purified populations of Tmt-positive cells obtained by fluorescent activated cell sorting (FACS). HDC expression within these FACS-separated cells was found to coincide with other markers of both ECL cells and mast cells. Gastrin expression was co-localized with HDC expression in a subset of histaminergic gastric mucosal cells. We suggest that these transgenic mice will facilitate future studies aimed at investigating the function of histamine-producing cells.

A biochemical study on the gastroprotective effect of andrographolide in rats induced with gastric ulcer

The major objective of the study was to evaluate the gastroprotective property of andrographolide, a chief component of the leaves of Andrographis paniculata in terms of the ulcer preventive effect in rats. An acute toxicity test was conducted with different concentrations of andrographolide to determine the LD₅₀ value. The dose responsive study was conducted in rats pretreated with andrographolide (1, 3 and 5 mg/kg) for a period of 30 days, prior to ulcer induction by administering ethanol, aspirin or by pyloric ligation. The ulcer protective efficacy was tested by determining the ulcer score, pH, pepsin, titrable acidity, gastric mucin, lipid peroxides, reduced glutathione, and enzymatic antioxidants superoxide dismutase, catalase and glutathione peroxidase in gastric tissue. The activities of H⁺-K⁺ ATPase and myeloperoxidase were also determined in gastric tissue. The LD₅₀ value was found to be 48 mg/kg b. wt and the effective dose was found to be 3 mg/kg. We have observed a significant reduction in the ulcer score in rats pretreated with 3 mg of andrographolide/kg body weight. A favourable increase in the pH and decrease in titrable acidity were observed in the gastric fluid of rats pretreated with the test drug. The gastric tissue H⁺-K⁺ ATPase and myeloperoxidase activities were elevated in ulcer-induced animals. The elevation in the enzyme activity was significantly minimized in the andrographolide received animals. The antioxidants and mucin levels were significantly maintained in the gastric tissue of drug-pretreated animals. Andrographolide did not produce any toxic effects in normal rats. This study reveals that the ulcer preventive efficacy of andrographolide may probably due to its antioxidant, cytoprotective and antiacid secretory effects.

Acute, sub-chronic oral toxicity studies and evaluation of antiulcer activity of Sooktyn in experimental animals

Sooktyn (SKN), mineralo-herbal drug which is being used largely by the patients for its extremely good therapeutic value to treat the gastric ulcers. The present study was undertaken to evaluate the toxicity studies and antiulcer activity of SKN. Acute and sub-chronic toxicities were studied in male and female Wistar rats. A single acute SKN of 2 000 mg/kg was administered by oral gavage for acute toxicity. Sub-chronic doses were 400 and 800 mg/kg/day. The major toxicological end points examined included animal body weight and food intake, selected tissue weights, and detailed gross necropsy. In addition, we examined blood elements: hematocrit, hemoglobin concentration, erythrocyte count, total leukocyte count and MCH, MCHC and platelets as well as biochemical parameters: urea, sugar, alanine transaminase, aspartate transaminase, alkaline phosphatase, total proteins, and creatinine. Also, anti-ulcer activity was carried out by employing indomethacin, ethanol, pylorus ligation, and hypothermic-stress-induced ulcer models. LD₅₀ may be greater than 2 000 mg/kg (orally) for SKN and there were no signs of toxicity on 28 days sub-chronic oral administration of 400 and 800 mg/kg of SKN in rats on the basis of blood elements and biochemical parameters. The ulcer indices decrease in all ulcer models with 66.62%, 61.24%, 80.18%, and 74.76% in indomethacin, ethanol, pylorus ligation, and hypothermic-stress-induced ulcer models, respectively. The results suggest that SKN has no signs of toxicity at 2 000 mg/kg body weight of rats orally; sub-chronically. The drug is safe and has antiulcer activity.

Gastroprotective activity of the ethanolic extract and hexane phase of Combretum duarteanum Cambess. (Combretaceae)

Combretum duarteanum Cambess. is found in South America, particularly in Bolivia, Paraguay, and Brazil. In Paraiba state (Brazil), the species usually occurs in the Caatinga biome. It is popularly known as mofumbo, cipiúba, or cipaúba. This work aims to evaluate the gastroprotective activity and the cytoprotective mechanisms of the ethanolic extract (Cd-EtOHE) and hexane phase (Cd-HexP) obtained from the leaves of C. duarteanum. Doses at 62.5, 125, 250, and 500 mg/kg of Cd-EtOHE and Cd-HexP were tested in models of gastric ulcers induced by HCl/ethanol, absolute ethanol, stress, non-steroidal anti-inflammatory drugs, and pylorus ligation in male rats or mice. Cd-EtOHE and Cd-HexP significantly reduced gastric injuries induced in all models. Cd-EtOHE and Cd-HexP did not alter gastric juice parameters such as pH, [H(+)], or volume after pylorus ligation. Cytoprotective mechanisms of Cd-EtOHE and Cd-HexP in relation to mucus, nitric oxide (NO), and sulfhydryl (SH) groups were evaluated. Neither product increased the mucus, and they both showed dependence on NO and SH groups to prevent gastric ulcer. Both Cd-EtOHE and Cd-HexP demonstrated gastroprotective activity.

Rebound acid hypersecretion after withdrawal of gastric acid suppressing drugs: new evidence of similitude

BACKGROUND

Homeopathy is based on the principle of similitude (similia similibus curentur) using medicines that cause effects similar to the symptoms of disease in order to stimulate the reaction of the organism. Such vital, homeostatic or paradoxical reaction of the organism is closely related to rebound effect of drugs.

METHOD

Review of the literature concerning the rebound effects of drugs used to suppress gastric acidity, particularly proton pump inhibitors (PPIs).

RESULTS

The mechanism of action of these effects is discussed. Rebound in terms of clinical symptoms and physiological effects occur in about 40% of people taking PPIs, their timing depends on the half-life of the drug and the adaptation period of the physiological mechanisms involved. The wide use of PPIs may be linked to the rising incidence of carcinoid tumours.

CONCLUSIONS

These findings support Hahnemann's concept of secondary action of drugs. We are developing a homeopathic materia medica and repertory of modern drugs on the basis of reported rebound effects.

Gastroprotective activity of Trichosanthes cucumerina in rats

AIM OF THE STUDY

The aim of the present study was to scientifically investigate whether Trichosanthes cucumerina Linn (Family: Cucurbitaceae) has gastroprotective activity.

MATERIALS AND METHODS

All the experiments were conducted using Wistar strain rats (weight: 200-220 g). The food and water given to rats was withdrawn for 36 and 12h respectively, before the commencement of the experiment. These rats were randomly divided into 6 groups (n=8 rats/group; 4 males+4 females) and groups 1-3 were orally administrated with hot water extract (HWE) at a dose of 375, 500 and 750 mg/kg, respectively. Group 4 was orally treated with equal volume of distilled water (1 mL; control), group 5 was orally treated with a reference drug, cimetidine (100mg/kg) while the group 6 was orally treated with another reference drug, sucralfate (400mg/kg). In the indomethacin experiment, only one dose of HWE (750 mg/kg) was tested, as this was found to have the maximum effect in the alcohol model also.

RESULTS

Results show that the HWE of Trichosanthes cucumerina possesses significant (P<or=0.05) and dose dependent gastroprotective effects in the alcohol model in terms of the length and number of gastric lesions mediated by alcohol, with a maximum effect at 750 mg/kg (inhibition of lesion length by 92%; number of gastric lesions by 88%). The same dose also mediated a significant (P<or=0.05) gastroprotective activity in the indomethacine model (inhibition of lesion length by 88%; number of gastric lesions by 84%). In both models, the protective effect demonstrated by the HWE was comparable with that produced by cimetidine. The HWE significantly (P<or=0.05) increased the amount of mucus produced by the rat gastro mucosa (by 39%) and reduced the gastric acidity (total acidity by 36%; free acidity by 40%). pH of the gastric juice increased from 4.1 to 6.0. However, no change in the volume of gastric juice was observed. Further, HWE showed potent antihistamine activity.

CONCLUSION

It may be concluded that HWE of Trichosanthes cucumerina exerts a significant protection against ethanol or indomethacin induced gastric damage. Increasing the protective mucus layer, decreasing the acidity of the gastric juice and antihistamine activity are probable mechanisms by which the HWE of Trichosanthes cucumerina mediates its gastroprotective actions.

Measurement of the intracellular ph in human stomach cells: a novel approach to evaluate the gastric acid secretory potential of coffee beverages

As the consumption of coffee beverages sometimes is reported to cause gastric irritation, for which an increased stomach acid secretion is one of the promoting factors, different processing technologies such as steam-treatment have been developed to reduce putative stomach irritating compounds. There is evidence-based data neither on the effect of detailed processing variations nor on individual coffee components affecting the proton secretory activity (PSA). This work aimed at developing a screening model suitable for investigating the effects of commercial coffee beverages and components thereof on human parietal cells. Human gastric cancer cells (HGT-1) were treated with reconstituted freeze-dried coffee beverages prepared from customary coffee products such as regular coffee (RC, n = 4), mild bean coffee (MBC, n = 5), stomach friendly coffee (SFC, n = 4), and SFC decaffeinated (SFCD, n = 3). PSA was analyzed by flow cytometry using the pH-sensitive dye SNARF-AM. Treatment of the cells with MBC did not result in a PSA different from RC treatment (p <or= 0.07), whereas cells treated with SFC (p <or= 0.04) or SFCD (p <or= 0.03) showed a significantly lower PSA than those treated with RC. Quantitative and principle component analysis of putative stomach irritating compounds revealed significantly reduced contents of (beta)N-alkanoyl-5-hydroxytryptamides, caffeine, N-methylpyridinium, and catechol in SFCD compared to RC. However, none of these compounds seem to act as the sole key bioactive reducing the PSA of SFCD, since their contents in MBC and SFC samples were not different from those in RC samples, although the PSA of these beverages was significantly lower than that of reconstituted freeze-dried RC beverage.

Clinical use of proton-pump inhibitors but not H2-blockers or antacid/alginates raises the serum levels of amidated gastrin-17, pepsinogen I and pepsinogen II in a random adult population

OBJECTIVE

Proton-pump inhibitors (PPIs), H(2) receptor antagonists (H(2)RAs) and antacids/alginates reduce intragastric acidity and may thus influence normal gastric physiology. The purpose of this study was to examine the effect of these compounds on serum levels of amidated gastrin-17 (G-17) and pepsinogens (PGI & PGII) in a large, random, adult Swedish population sample with uninfected stomach mucosa.

MATERIAL AND METHODS

The initial sample subjects (n=1000, mean age 50 years, range 20-80 years) completed a questionnaire on the use of acid inhibitory drugs 1 week and/or 3 months before study entry. All subjects (n=590) with normal gastric mucosa as delineated by serum biomarkers were included. Among them, serum levels of PGI, PGII and G-17 were compared between those who used acid inhibitory drugs and those who did not.

RESULTS

The serum levels of G-17 or pepsinogens in the subjects who reported use of H(2)RAs (n=18) or antacid/alginates (n=66) during the previous 3 months did not differ from those in non-users (n=471). However, the median levels of G-17 and pepsinogens were significantly (p<0.001) higher among the PPI users (n=35) than among non-users: the levels were approximately doubled. The ratio of PGI/PGII was, however, similar between PPI users and non-users, or those using antacids/alginates or H(2)RAs. Among subjects using PPIs, the serum levels of pepsinogens correlated positively (p<0.01) with the serum levels of G-17.

CONCLUSIONS

PPIs but not antacids/alginates or H(2)RAs markedly increase the fasting levels of serum amidated G-17 and pepsinogens among ordinary patients in everyday clinical practice.

Antiulcerogenic effect of Securigera securidaca L. seed extract on various experimental gastric ulcer models in rats

Securigera securidaca belongs to the family Fabaceae is used in Iranian folk medicine to treat gastric disturbances. The present study was undertaken to evaluate the Securigera securidaca seed hydroalcoholic extract (SSE) and its subfractions for their gastroprotective effect in rat. Acute gastric ulceration in rats was produced by oral administration of ethanol (100%; 1 mL/200 g of body weight) or water immersion restraint-stress (5 h, water immersion restraint stress at 20-22 degrees C). Ranitidine (100 mg kg(-1), p.o.) was used as the reference antiulcer drug. After ethanol administration, the gastric wall mucus was examined. Chronic gastric ulceration was produced by injection of acetic acid in rat gastric subserosa. The antisecretory effect of the extract and its subfractions (ethyl acetate, chloroform and aqueous fractions) were investigated in pylorus-ligated rats. Administration of SSE significantly inhibited gastric mucosa damage induced by ethanol, water immersion restraint-stress and acetic acid in a dose-dependent manner. In pylorus ligature rats, SSE and its subfractions significantly reduced the basal gastric acid secretion and total acidity; moreover, it inhibited the increase in total acidity induced by carbachol. However, the antisecretory effect of the chloroform fraction was more potent than two other fractions. Administration of SSE did not affect the gastric mucus production. The results obtained in the present study indicate that the SSE has gastroprotective and antisecretory effects on gastric mucosa in rats.

Antiulcerogenic activity of bark extract of Tabebuia avellanedae, Lorentz ex Griseb

Tabebuia avellanedae is commonly used for the treatment of peptic ulcers. We carried out this study with the ethanolic extract of bark from Tabebuia avellanedae (EET) (30-1000 mg/kg) to determine its gastroprotective activity and to clarify the pathways involved in this effect. Acute gastric ulceration in rats was produced by oral administration of ethanol and ibuprofen. After ethanol administration, the gastric wall mucus was examined. Chronic gastric ulceration was produced by injection of acetic acid in rat gastric subserosa. Anti-secretory studies were undertaken using Shay rat pylorus ligature technique and measurement of enzymatic activity of H+, K+-ATPase in vitro. Administration of EET p.o. or i.p. significantly inhibited gastric mucosa damage induced by ethanol and ibuprofen. The anti-ulcer effect was further confirmed by enhanced gastric mucus production. In pylorus ligature rats, EET significantly reduced the basal gastric acid secretion and total acidity; moreover, it inhibited the increase in total acidity induced by histamine. In addition, EET reduced the activity of H+, K+, ATPase. The results obtained in the present pharmacological assay indicate that this plant has a protective action against gastric lesions, involving the maintenance of protective factors, such as mucus and prostaglandin, besides the reduction of gastric total acidity.

Further evidence for a C-terminal structural motif in CCK2 receptor active peptide hormones

A comparison of the conformational characteristics of the related hormones [Nle(15)] gastrin-17 and [Tyr(9)-SO(3)] cholecystokinin-15, in membrane-mimetic solutions of dodecylphosphocholine micelles and water, was undertaken using NMR spectroscopy to investigate the possibility of a structural motif responsible for the two hormones common ability to stimulate the CCK(2) receptor. Distance geometry calculations and NOE-restrained molecular dynamics simulations in biphasic solvent boxes of decane and water pointed to the two peptides adopting near identical helical C-terminal configurations, which extended one residue further than their shared pentapeptide sequence of Gly-Trp-Met-Asp-Phe-NH(2). The C-terminal conformation of [Nle(15)] gastrin-17 contained a short alpha-helix spanning the Ala(11)-Trp(14) sequence and an inverse gamma-turn centered on Nle(15) while that of [Tyr(9)-SO(3)] cholecystokinin-15 contained a short 3(10) helix spanning its Met(10) to Met(13) sequence and an inverse gamma-turn centered on Asp(14). Significantly, both the C-terminal helices were found to terminate in type I beta-turns spanning the homologous Gly-Trp-Met-Asp sequences. This finding supports the hypothesis that this structural motif is a necessary condition for CCK(2) receptor activation given that both gastrin and cholecystokinin have been established to follow a membrane-associated pathway to receptor recognition and activation. Comparison of the conformations for the non-homologous C-terminal tyrosyl residues of [Nle(15)] gastrin-17 and [Tyr(9)-SO(3)] cholecystokinin-15 found that they lie on opposite faces of the conserved C-terminal helices. The positioning of this tyrosyl residue is known to be essential for CCK(1) activity and non-essential for CCK(2) activity, pointing to it as a possible differentiator in CCK(1)/CCK(2) receptor selection. The different tyrosyl orientations were retained in molecular models for the [Nle(15)] gastrin-17/CCK(2) receptor and [Tyr(9)-SO(3)] cholecystokinin-15/CCK(1) receptor complexes, highlighting the role of this residue as a likely CCK(1)/CCK(2) receptor differentiator.

The gastroprotective effect of the essential oil of Croton cajucara is different in normal rats than in malnourished rats

It has been shown previously that malnourished rats are resistant to acute gastric lesions but not to subchronic gastric ulceration. It also has been demonstrated that the essential oil obtained from the bark of Croton cajucara (Sacaca) has antiulcer properties. In the present study, the ability of this essential oil to prevent the formation of gastric ulcers in rats fed a diet with 17% protein (normoproteic rats) or 6% protein (malnourished rats) was investigated. At a dose of 100mg/kg body weight, orally, the essential oil significantly reduced the gastric injury caused by indomethacin (25% after 2h and 70% after 4h) only in normoproteic rats. In the pylorus ligature model, the essential oil increased the pH and gastric volume, but decreased the total acid concentration in both groups when compared to the respective control group. The essential oil significantly increased prostaglandin E2 production in glandular cells by 50% compared to the controls in both groups of rats. In addition, the amount of gastric mucus was two-fold higher in malnourished rats than in normoproteic rats. The present results show that the enhanced protective effect of essential oil in malnourished rats involved an increase in prostaglandin E2 production and mucus secretion, which are both factors that protect the gastric mucosa against damage. In agreement with this, malnourished rats always had a lower number of acute gastric ulcers.

Effect of somatostatin analogue octreotide injected into the third cerebral ventricle on pentagastrin-induced gastric acid secretion in rats

AIM: To investigate the effect of long-lasting somatostatin analogue octreotide (Oct) injected into the third cerebral ventricle (TCV) on gastric acid secretion in rats.

METHODS: TCVs were cannulated in male Wistar rats anesthetized with sodium pentobarbital. One week later acute gastric lumen perfusion was carried out and gastric acid was continuously washed with 37°C saline by a perfusion pump. Gastric perfusion samples were collected every 10 min and titrated by 0.01 moL/L NaOH to neutral. On the basis of subcutaneous (sc) injection of pentagastrin (G-5, 160 μg/kg), Oct (0.025 μg, 0.05 μg, 0.1 μg, n = 12 in each group) or vehicle (pyrogen-free physiological saline, n = 10) was injected into the TCV. Before and after the TCV injection, 1 h total acid output (TAO) was determined and experimental data were expressed in change rate (%) of TAO.

RESULTS: Oct (0.025, 0.05 and 0.1 μg) injected into the TCV resulted in change rate of 1.56% (P > 0.05), 20.21% (P <  0.01) and 37.82% of TAO (P <  0.001), respectively. Moreover, comparison in change rate of TAO among these 3 doses showed P <  0.05 between 0.025μg and 0.05 μg, P <  0.01 between 0.025 μg and 0.1μg, and P <  0.05 between 0.05μg and 0.1 μg. However, sc injection of 0.05 μg Oct had no effect on G-5 stimulated gastric acid secretion.

CONCLUSION: Octreotide injected into the third cerebral ventricle inhibits gastrin-induced gastric acid secretion in a dose-dependent manner.

Isoliquiritigenin selectively inhibits H(2) histamine receptor signaling

Isoliquiritigenin, one of the major constituents of Glycyrrhiza uralensis (licorice), is a natural pigment with a simple chalcone structure 4,2',4'-trihydroxychalcone. In this study, isoliquiritigenin showed selective H(2) histamine receptor (H(2)R) antagonistic effect and remarkably reduced several H(2)R-mediated physiological responses. Preincubation of U937 and HL60 hematopoietic cells with isoliquiritigenin significantly inhibited H(2)R agonist-induced cAMP response in a concentration-dependent manner without affecting the viability of cells. Isoliquiritigenin also blocked the binding affinity of [(3)H]tiotidine to membrane receptors in HL-60 cells. Isoliquiritigenin did not affect the elevation of cAMP levels induced by cholera toxin, forskolin, or isoproterenol, indicating that the action site of isoliquiritigenin is not G(s) protein, effector enzyme, adenylyl cyclase, or beta(2)-adrenoceptor. Isoliquiritigenin affected neither H(1)R-nor H(3)R-mediated signaling. In molecular docking studies, isoliquiritigenin exhibited more favorable interactions with H(2)R than histamine. Isoliquiritigenin prominently inhibited H(2)R selective agonist dimaprit-induced cAMP generation in MKN-45 gastric cancer cell. Moreover, isoliquiritigenin reduced gastric acid secretion and protected gastric mucosal lesion formation in pylorus-ligated rat model. Taken together, the results demonstrate that isoliquiritigenin is an effective H(2)R antagonist and provides the basis for designing novel H(2)R antagonist.