Effects of zinc acexamate on gastric mucosal resistance factors

Development and Validation of a Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of ε-Acetamidocaproic Acid in Rat Plasma

A simple and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of ε-acetamidocaproic acid (AACA), the primary metabolite of zinc acexamate (ZAC), in rat plasma by using normetanephrine as an internal standard. Sample preparation involved protein precipitation using methanol. Separation was achieved on a Gemini-NX C18 column (150 mm × 2.0 mm, i.d., 3 μm particle size) using a mixture of 0.1% formic acid-water : acetonitrile (80 : 20, v/v) as the mobile phase at a flow rate of 200 μl/min. Quantification was performed on a triple quadrupole mass spectrometer employing electrospray ionization and operating in multiple reaction monitoring (MRM) and positive ion mode. The total chromatographic run time was 4.0 min, and the calibration curves of AACA were linear over the concentration range of 20~5000 ng/ml in rat plasma. The coefficient of variation and relative error at four QC levels were ranged from 1.0% to 5.8% and from -8.4% to 6.6%, respectively. The present method was successfully applied for estimating the pharmacokinetic parameters of AACA following intravenous or oral administration of ZAC to rats.

Anti-ulcer Activity of a Slow-release Zinc Complex, Zinc Monoglycerolate (Glyzinc)

A slow-release zinc complex, zinc monoglycerolate (ZMG) was examined for its potential gastroprotective activity in various gastric ulcer models. These models comprised (a) oral or parenteral nonsteroidal anti-inflammatory drugs (NSAIDs) given to rats whose gastrointestinal mucosa was pre-sensitized by prior development of arthritis, oleyl alcohol-induced inflammation and cold exposure, (b) oral ethanol (12·5−100%) with and without added 4% HCl, (c) intraperitoneal reserpine (5 mg kg−1) in arthritic and normal rats and in normal mice, (d) oral NSAIDs given to mice in which acid and pepsin production was stimulated by co-administration of intraperitoneal bethanechol chloride (5 mg kg−1) to enhance ulcer development, and (e) NSAIDs given to carrageenan-inflamed rats to determine effects of ZMG on paw inflammation. In these models, ZMG given orally was effective in preventing development of gastric lesions, except with propionic acid NSAIDs; the effective doses being apparently dependent on the severity of the mucosal injury. In many of the models ZMG was superior to zinc sulphate and other zinc salts or metal ion complexes investigated but was slightly more effective or equipotent compared with zinc acexamate. ZMG did not impair the anti-oedemic effects of NSAIDs. ZMG is thus an effective agent in preventing ulcer development in a wide range of model systems and may be more effective than zinc salts because of the controlled slow-release of zinc from the complex.

Influence of dietary zinc and copper on digestive enzyme activity and intestinal morphology in weaned pigs1

The current study was conducted to investigate the effects of high dietary concentrations of Zn as zinc oxide and Cu as copper sulfate on the activity of digestive enzymes in the pancreas and the intestinal mucosa, intestinal morphology, and mucin histochemistry in pigs after weaning. Thirty-two pigs were weaned at 4 wk of age. The pigs were fed standard weaning diets supplemented with Zn (100 or 2,500 ppm) and Cu (0 or 175 ppm) in a 2 x 2 factorial arrangement of treatments for a 14-d period. In pancreatic tissue, the activity of amylase, carboxypeptidase A, chymotrypsin, trypsin, and lipase increased (P < 0.01) in pigs fed 2,500 ppm of Zn, whereas the activity of carboxypeptidase B and carboxylester hydrolase was unaffected. Copper had no effect on the activity of pancreatic enzymes. In small intestinal contents, the total activity of amylase and carboxypeptidase A was greater in pigs fed 100 ppm of Zn (P < 0.05), whereas feeding 2,500 ppm of Zn increased the chymotrypsin activity (P < 0.001). The remaining enzymes were unaffected by dietary Zn concentration. The villi were longer in the cranial small intestine (P < 0.001) in pigs fed 100 ppm of Zn than in pigs fed 2,500 ppm of Zn, but otherwise there were no clear effects of Zn and Cu supplementation on intestinal morphology. In the cranial small intestine, the activity of maltase (P < 0.001), sucrase (P < 0.001), and lactase was greater in pigs fed 100 ppm of Zn, even though there was a Zn x Cu interaction (P < 0.05) in lactase activity. In the middle and caudal small intestine, no clear differences between dietary treatments were observed. The activity of gamma-glutamyl transpeptidase in the intestinal mucosa was not affected by dietary Zn or Cu. In pigs fed 100 ppm of Zn, the activity of aminopeptidase N was greater in the caudal small intestine, but dietary Zn or Cu had no effect on aminopeptidase N in the cranial and middle small intestine. No effect of dietary Zn or Cu supplementation was found on carbohydrate histochemistry in the caudal small intestine, whereas high dietary Zn increased the area of neutral, acidic, and sulfomucins in the cecum (P < 0.01) and in the colon (P < 0.001). In summary, high dietary Zn increased the activity of several enzymes in the pancreatic tissue and increased the mucin staining area in the large intestine, whereas Cu had no clear effect on these variables. However, no definite answers were found as to how the growth promoting and diarrhea reducing effects of excess dietary Zn are exerted.

Evaluation of antinociceptive, anti-inflammatory and antiulcerogenic activities of Maytenus ilicifolia

Maytenus ilicifolia (Celastraceae) is a native plant from Tropical Atlantic Forest (Mata Atlântica, Brazil) called 'espinheira-santa'. This plant is traditionally used as anti-inflammatory, analgesic and antiulcerogenic. Many studies focusing pharmacological and toxicological aspects of the plant have been performed. The aim of this study is to evaluate the efficacy (anti-inflammatory and antinociceptive activities and protection against gastric lesions, including cytoprotection and healing) and phytochemical profile of hexane and ethylacetate extracts of Maytenus ilicifolia. Per os administration of these extracts inhibited nociception and formaldehyde-induced paw oedema in mice and carrageenin-induced paw oedema in rats. Severity of gastric lesions induced by cold-restraint stress (-18 degrees C for 45 min) method was also clearly reduced in rats considering both cytoprotection and healing aspects. Administration of the extracts led to volume gastric and pH increase. These results suggest that hexane and ethylacetate extracts of Maytenus ilicifolia may represent an important clinical alternative in anti-inflammatory and antiulcerogenic therapeutics, though, further experiments should be performed to confirm this assertion.

Anti-inflammatory activity and gastric lesions induced by zinc-tenoxicam

Oral administration of tenoxicam or zinc-tenoxicam complex inhibited to a similar extent carrageenin-induced paw oedema and granulomatous tissue formation in rats as well as the acetic acid induced writhing response in mice. Gastric lesions induced by oral administration of zinc-tenoxicam were reduced in number and severity when compared with those induced by tenoxicam or the co-administration of tenoxicam and zinc acetate. However, after intraperitoneal administration, both zinc-tenoxicam and tenoxicam plus zinc acetate induced a reduced number of gastric lesions as compared with tenoxicam.

Effect of D-002 on gastric mucus composition in ethanol-induced ulcer

This study was designed to determine the effect of D-002, a natural product isolated and purified from beeswax (Apis mellifera), on gastric mucus composition on ethanol-induced ulcer in rats. The morphology of the lesions was analysed histologically, and morphometric analysis of gastric-gland content in total glycoprotein and sulphated macromolecules were done. Oral pretreatment with D-002 at 5 and 25 mgkg(-1)1 before oral administration of ethanol at 60%, produced a significant increase in the amount of gastric mucus and total protein. The histomorphometric evaluation of the gastric damage at the same doses showed a significant increase in neutral glycoproteins and sulfated macromolecules. It is concluded that enhancement of the quantity and quality of the mucus could partly explain the gastroprotective effect of D-002.

Protective effects of zinc in indomethacin-induced gastric mucosal injury: evidence for a dual mechanism involving lipid peroxidation and nitric oxide

BACKGROUND

Indomethacin causes gastric mucosal injury, although the pathogenesis is not fully understood. Zinc, is known to have gastroprotective effects in both humans and experimental animals.

AIM

To determine (i) the protective effects of zinc in indomethacin-induced gastric mucosal injury in rats, and (ii) whether these cytoprotective effects are mediated by changes in gastric lipid peroxidation and/or nitric oxide synthase activity.

METHODS

Gastric lesions were induced in rats by the intragastric administration of indomethacin. Morphological changes, lipid peroxidation (malondialdehyde levels) and nitric oxide synthase activity were determined in animals pre-treated with zinc sulphate and in controls.

RESULTS

Indomethacin significantly increased malondialdehyde levels and decreased NOS activity. These effects were attenuated by pre-treatment with zinc (P < 0.005 and 0.0001, respectively). The protective effects of zinc were readily abolished in animals pre-treated with N-nitro-L-arginine methyl ester (L-NAME). Morphologically, indomethacin induced large areas of mucosal ulcerations, which were completely prevented by zinc pre-treatment.

CONCLUSIONS

Zinc provides protection against indomethacin-induced gastric mucosal injury. These protective effects result from the inhibition of lipid peroxidation and the preservation of mucosal nitric oxide synthase.

Aspirin-like drugs cause gastrointestinal injuries by metallic cation chelation

Aspirin-like (nonsteroidal anti-inflammatory) drugs may cause injuries including ulcers to the gastrointestinal tract by chelation of the divalent and/or multivalent metallic cations in the gastrointestinal mucus and mucosa, as suggested by the chemical properties of these drugs and supported by experimental and clinical data.

Effects of cisapride on ulcer formation and gastric secretion in rats: comparison with ranitidine and omeprazol

1. The antiulcerogenic effects of cisapride, a potent benzamide-stimulating gastrointestinal motility agent, were studied on cold-resistant and pylorus-ligated gastric ulcers. Acidity, composition of gastric secretion, and quantitative and qualitative changes on mucus glycoprotein content were also determined. These effects were compared with those of ranitidine (50 mg/kg) and omeprazol (10 mg/kg). 2. Oral cisapride (10-100 mg/kg) dose-relatedly and significantly (P < 0.01, P < 0.05) decreased the severity of the lesions induced by cold-resistant stress. In stressed rats, cisapride increased the amount of mucus secretion and markedly enhanced the glycoprotein content. Morphometric evaluation of mucus secretion revealed a significant increase in both the PAS area (neutral glycoproteins) and Alcian blue area (sulfated glycoproteins). 3. In 4 h pyloric-ligated animals, cisapride (10-100 mg/kg) showed a significant reduction in the number and severity of ulcers (P < 0.01) and histamine concentration (P < 0.01, P < 0.001). In addition, at the highest doses (50-100 mg/kg), cisapride produced a significant decreases in acidity; however, it did not alter the gastric volume secretion or pepsin concentrations. 4. These results suggest that cisapride shows antiulcerogenic effects which could possibly be explained through antisecretory and cytoprotective mechanisms involving an enhancement of cuality and production of gastric mucus.

Endogenous zinc concentrations in cysteamine-induced duodenal ulcers in the rat

Exogenously administered zinc compounds have been shown to possess anti-ulcer activity against a wide variety of ulcerogenic agents, both in laboratory animal models and in human peptic ulcer disease. However, a strong possibility exists that endogenous zinc may also play an important role during noxious events by various mechanisms. Therefore, the aim of this study was to focus on the changes of endogenous zinc serum and tissue concentrations in cysteamine-induced duodenal lesions. We used atomic absorption spectrophotometry to determine the tissue and serum concentrations of zinc in normal (control) rats and those with cysteamine-induced duodenal ulcers. The results obtained in this study indicated that the onset, development and spontaneous healing of ulcer lesions were associated with certain shifts in zinc serum and tissue concentrations. Prior to ulcer formation, a significant increase was noted in serum zinc values. With the onset of duodenal lesions, zinc serum concentrations significantly decreased, while there was a significant increase in duodenal tissue concentrations when compared to healthy control animals. Zinc tissue concentrations decreased and returned to starting values by the end of the first week of spontaneous healing. This decrease in zinc tissue concentration corresponded to the healing rate of the duodenal ulcers. Serum zinc concentrations also returned to starting values within the first week period. These observations indicate and confirm that zinc could play an important role in duodenal ulcer disease and represent a natural defense system in the body.

Cytoprotective and antisecretory activity of a ranitidine-zinc complex

The effects of a ranitidine-zinc complex and ranitidine alone were compared in three different experimental models (pyloric ligation, ethanol and indomethacin) of gastric ulceration in the rat. In the pyloric ligation model, the ranitidine-zinc complex (50, 100 and 150 mg/kg p.o.) showed antiulcerogenic activity similar to that observed with equimolar doses of ranitidine (35, 70 and 105 mg/kg p.o.). Both the ranitidine-zinc complex and ranitidine significantly reduced (p < 0.05) gastric acid secretion in a dose-dependent manner. The protective effect of the ranitidine-zinc complex (100 and 150 mg/kg p.o.) against gastric damage developing after p.o. administration of absolute ethanol or indomethacin was enhanced (p < 0.05) with respect to that obtained with equimolar doses of ranitidine (70 and 105 mg/kg p.o.). The presence of zinc in the ranitidine-zinc complex does not interfere with the antisecretory effects of ranitidine on the gastric mucosa, while it confers an additional cytoprotective action to the final compound.

Protection by almagate of ethanol-induced gastric mucosal damage in rats

The study was designed to analyse the protective effects of almagate on a model of gastric injury, ethanol-induced mucosal damage, in which acid plays little, if any, role. Pretreatment with almagate dose-dependently reduced the level of gastric damage induced by oral administration of 1 mL 100% ethanol. Administration of 12 mumol kg-1 alamagate 30 min before ethanol significantly reduced the area of mucosal damage by 65 +/- 10%, and the maximum level of inhibition (74 +/- 11%) was obtained with 150 mumol kg-1 almagate. Administration of higher doses of almagate (200-250 mumol kg-1) did not result in any further increase in the level of protection against ethanol-induced gastric damage. Administration of 1 mL 100% ethanol induces substantial damage to the gastric mucosa, with nearly 40% of the length of the section evaluated exhibiting deep necrotic and haemorrhagic damage. Pretreatment with almagate caused a significant diminution in all parameters of histological damage, whereas damage to the epithelial cell layer was only significantly reduced by pretreatment with the highest doses evaluated (25, 50 and 150 mumol kg-1). Administration of aluminium hydroxide did not modify ethanol-induced mucosal damage, even at doses containing concentrations of aluminium higher than those present in gastroprotective doses of almagate. Pretreatment with sucralfate, another aluminium containing compound, at doses of 250 mumol kg-1 protected the mucosa, although lower doses did not. The present study has shown that almagate prevents ethanol-induced gastric mucosal damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastrotoxic activity and inhibitory effects on gastric mucosal PGE2 production with different non-steroidal anti-inflammatory drugs: modifications induced by pretreatment with zinc acexamate

Gastrotoxic activities of different non-steroidal anti-inflammatory drugs (NSAIDs) (diclofenac, indomethacin, ketoprofen, naproxen and piroxicam) administered per os were compared with their ability to inhibit gastric prostaglandin E2 (PGE2) synthesis in the rat. In a parallel study, effects of pretreatment with zinc acexamate (ZAC) were also assessed. NSAIDs invariably caused gastric mucosal damage and a decrease of PGE2 levels. A good correlation between the decrease of PGE2 levels and the index of gastric lesion (r = 0.41; p < 0.021) was observed when results obtained with the different NSAIDs were pooled. ZAC pretreatment significantly decreased the overall severity of lesions induced by NSAIDs. However, no correlation between gastric lesion index and depletion of PGE2 gastric levels was observed after treatment with ZAC (r = 0.012; p < 0.948). These data corroborate the hypothesis that preservation of the capability to synthesize endogenous PGs is of critical importance in the maintenance of gastric mucosal integrity. The gastroprotective action observed with ZAC involves alternative mechanisms other than modification of PGE2 levels.

Antiulcerogenicity of the flavonoid fraction from Bidens aurea: comparison with ranitidine and omeprazole

Effects of the flavonoid fraction of Bidens aurea (Aiton) Sherff on gastric ulceration induced by restraint and cold were studied in rats. Mucosal damage was evaluated histomorphometrically and the results were compared with those of omeprazole and ranitidine. The effects of these agents on the quantity and quality of the gastric mucus were also determined histologically and biochemically. Oral treatment with the ether fraction of the flavonoid extract gave the highest level of gastric protection. Mucus content was increased and accompanied by a proportional increase in proteins and hexosamines. There was also a marked increase of the periodic acid-Shiff (PAS) area (neutral glycoprotein) and the alcian blue (AB) area (sulphated glycoprotein). The groups which received ranitidine and omeprazole did not overcome the inhibition of the mucus secretion induced in this experimental model.

Gastroprotective effect of zinc acexamate against damage induced by nonsteroidal antiinflammatory drugs. A morphological study

The gastroprotective effect of zinc acexamate against gastric damage induced by different nonsteroidal antiinflammatory drugs (indomethacin, diclofenac, and piroxicam) was morphologically assessed in the rat glandular stomach by light and scanning electron microscopy. In addition, the capability of these antiinflammatory drugs to inhibit gastric prostaglandin E2 production was compared with their ability to induce gastric lesions. Microscopically, disappearance of mucus glycoprotein and exfoliation of the mucosal surface were the most common findings. Surface ultrastructural lesions varied from minimal lesions of the surface epithelial cells to deep erosions of the gastric mucosa with release of associated cellular elements and sloughing of the denuded lamina propria. Diclofenac elicited the most powerful inhibitory activity on mucosal prostaglandin E2 (98% inhibition vs control), closely followed by piroxicam (97.8%) and indomethacin (91.05%). Pretreatment of animals with zinc acexamate significantly increased the presence of mucus glycoprotein, maintained the continuity of the surface epithelial cells, and decreased the depth of the mucosal erosions. The degree of protection exerted by zinc acexamate varied with the antiinflammatory, but was always evident.

Effect of zinc acexamate on gastric lesions induced by aspirin: a morphological study

The morphology of gastric lesions induced by aspirin in the rat and their modification by pretreatment with zinc acexamate (100 mg/kg) were studied by scanning electron microscopy. The influence of mucosal levels of prostaglandin E2 (PGE2) on the development of these lesions was also investigated. High (200 mg/kg) or low (50 mg/kg) doses of aspirin inhibited PGE2 production similarly, but the morphology of these lesions differed considerably. While gross exfoliation of extensive areas of gastric mucosa was observed after 200 mg/kg aspirin, only ultrastructural lesions of surface epithelial cells were present after 50 mg/kg aspirin. Regardless of the dose of aspirin administered, pretreatment with zinc acexamate raised PGE2 levels and increased the presence of mucus. Our results showed that after zinc acexamate, the development of deep erosions appearing with high doses of aspirin was prevented and the ultrastructural lesions induced by low doses of aspirin were not observed. The fact that zinc acexamate did not modify the anti-inflammatory action of aspirin in the carrageenin-induced oedema model suggests that the protective effect of zinc acexamate is exerted locally on the gastric mucosa.

Effects of zinc L-carnosine on gastric mucosal and cell damage caused by ethanol in rats. Correlation with endogenous prostaglandin E2

The effects of zinc L-carnosine on ethanol-induced damage and the correlation of these effects with endogenous prostaglandin E2 were evaluated in rat gastric mucosa in vivo and in vitro. When given either intragastrically or intraperitoneally, zinc L-carnosine (10 or 30 mg/kg) prevented gross visible damage to gastric mucosa caused by ethanol without affecting the mucosal prostaglandin E2 level. This protective effect of zinc L-carnosine was not inhibited by indomethacin. Histological assessment showed that zinc L-carnosine inhibited deep mucosal necrosis, as did 16,16-dimethyl prostaglandin E2. Zinc L-carnosine (10(-6) or 10(-5) M) inhibited the damage caused by ethanol to gastric cells isolated from rat gastric mucosa in vitro; this effect was not inhibited by indomethacin. The results suggested that zinc L-carnosine protects the gastric mucosa and enhances cellular resistance to ethanol without the mediation of endogenous prostaglandins.

Zinc acexamate inhibits gastric acid and pepsinogen secretion in the rat

Pretreatment with zinc acexamate (25-100 mg kg-1 i.p.) inhibited acid and pepsinogen secretion in the pylorus-ligated rat. Zinc acexamate (5-50 mg kg-1 p.o.) also inhibited the increases in acid secretion induced by carbachol (10 micrograms kg-1) and 2-deoxy-D-glucose (200 mg kg-1) in the perfused stomach of the anaesthetized rat. A delayed antisecretory effect was observed with this drug on histamine induced responses. High concentrations of zinc acexamate (10(-5) - 10(-2) M) did not modify the in-vitro activity of pepsin. Administration of zinc acexamate resulted in an increase in the presence of pepsinogen at the mucosal level. A morphological examination of the gastric mucosa confirmed an accumulation of zymogen-containing granules in the gastric chief cells of zinc acexamate-treated rats (50 mg kg-1 p.o.). These results indicate that zinc acexamate decreases acid and pepsinogen secretion in-vivo, and this may explain its antiulcer activity.

Dual effects of zinc sulphate on ethanol-induced gastric injury in rats: possibly mediated by an action on mucosal blood flow

The present study examines the protective effect of zinc sulphate against ethanol-induced gastric mucosal ulcers in rats. Absolute ethanol decreased the gastric mucosal blood flow and produced haemorrhagic lesions in the glandular mucosa. Zinc sulphate preincubation in an ex-vivo stomach chamber preparation prevented the formation of ethanol-induced lesions and attenuated the decrease of blood flow produced by ethanol. Subcutaneous injection of the same doses of the drug at 15 and 30 min before ethanol exposure, markedly reduced the blood flow and also aggravated ethanol-induced gastric injury; however, when injected at 23 and 24 h before ethanol administration, zinc sulphate protected against lesion formation but had no effect on the vascular changes induced by ethanol in the gastric glandular mucosa. These findings show that the antiulcer effect of zinc sulphate occurs only when the drug is given orally, or injected s.c. 23 and 24 h before ethanol challenge. Furthermore, this protective action is probably not entirely mediated by preservation of the gastric mucosal blood flow.

Zinc acexamate reduces gastric damage induced by platelet-activating factor

We have tested the ability of zinc acexamate (ZAC) to prevent platelet-activating-factor (Paf) induced gastric damage in rats. Lesions were characterized by a vascular congestion affecting the entire mucosa, oedema, haemorrhage and frequent necrosis of the more superficial areas. The gastric damage appearing after Paf was accompanied by degranulation of gastric mast cells. Leukocytes were often seen at the submucosal level. Oral pretreatment with ZAC reduced in a dose-dependent manner both gastric damage and mast cell degranulation observed after Paf. ZAC administered orally at a dose of 100 mg kg-1 statistically inhibited (p less than 0.01) gastric damage and mast cell degranulation. ZAC did not affect the hypotension induced by Paf confirming that gastric damage and hypotension appearing in rats after Paf administration are two independent phenomena. The present findings indicate that the inhibitory effect of ZAC upon gastric lesions induced by Paf may be related to the different protective actions exhibited by this zinc compound in a wide variety of experimental models of gastric ulcer.

Effects of zinc acexamate on blood flow and prostanoid levels in the gastric mucosa of the rat

The effects of the new antiulcer compound zinc acexamate on blood flow and prostanoid levels in the gastric mucosa have been studied. Zinc acexamate (30 and 300 mg/kg) dose-dependently prevents the reduction induced by the perfusion of noradrenaline (3.5 micrograms/kg.min, 30 min) in gastric mucosal blood flow, as measured by 3H-aniline clearance. Zinc acexamate pretreatment also increases the levels of prostaglandin E2 in the gastric mucosa of the rat, both under control conditions and after infusion with noradrenaline. The levels of thromboxane A2 and prostacyclin were not modified by zinc acexamate. These results confirm the importance of microcirculation in pathogenesis and the idea that the antiulcer activity of zinc acexamate is due in part to its action in increasing the mechanism which defend the gastric mucosa against aggression.

Effects of zinc-aspartate and zinc-glycinate in healthy rats and on reserpine-induced gastric lesions

Experimental studies performed on 227 rats showed that Zn-aspartate and Zn-glycinate administered ip lowered the incidence, number, and severity of the reserpine-induced gastric lesions ensuring significant protection indices. Histochemical methods revealed increased amount of mucosal glycoproteins. The activity of dehydrogenases involved in energy metabolism that modulates acid secretion in the parietal cells was depressed. RNA content in the chief cells, as premises of pepsinogen synthesis, was decreased. ATPase reaction in the periglandular capillaries was uniform and stronger, showing an improvement of gastric mucosal microcirculation. Since these histochemical changes were also noted in healthy rats receiving Zn salts, it might be suggested that they are not the mere expression of an anti-ulcer protective effect of zinc, but rather reflect its mechanism of action, relating to the complex metabolic events induced by the trace element. Our results are in agreement with those previously reported concerning the noxious influence of Zn depletion, the accelerated healing of peptic ulcer patients after Zn treatment, and the protective effect of Zn against ulcerogenesis in several experimental models involving different pathomechanisms.

Effects of zinc acexamate on gastric mucosal production of prostaglandin E2 in normal and stressed rats

Changes in PGE2 levels induced by zinc acexamate (ZAC) at gastricmucosal level were assessed in a rat model. Experiments were performed in normal rats and rats subjected to cold-restraint stress and in experimental conditions in which prostaglandins (PGs) synthesis was inhibited by prior administration of indomethacin. Gastric injuries after different treatments were quantified macro and microscopically. Total amount of PGE2 and mucus material recovered from gastric mucosa were increased after ZAC treatment. Indomethacin aggravated gastric damage secondary to stress and inhibited PGE2 and mucus increase appearing after ZAC treatment. These data confirm the relation between PGE2, mucus production and gastric protection. ZAC 200 mg/kg was able to reduce the gastric damage induced by stress. This decrease was also evident in the group receiving indomethacin before ZAC administration. These experiments indicate that ZAC exhibits its antiulcer action by increasing prostaglandins but other mechanisms independent of PGs synthesis are also involved.

Effects of zinc sulphate on gastric mucosal blood flow and gastric emptying of the rat

Zinc sulphate (50 mg kg-1 p.o.) did not modify basal gastric mucosal blood flow, as measured by [3H]aniline clearance, but inhibited its reduction by noradrenaline (3.5 micrograms kg-1 min-1). Zinc sulphate also influenced gastric emptying of phenol red but its effects depended upon the dose; 30 mg kg-1 caused no variation whereas 80 mg kg-1 induced a significant delay. The nature of both actions is discussed and their implications in the development and prevention of gastric ulceration have been analysed.

Zinc deficiency: its role in gastric secretion and stress-induced gastric ulceration in rats

The effects of zinc deficiency on gastric secretion and on cold-restraint stress-induced ulceration in rat stomachs have been studied. Administration of graded zinc deficient diets for 5 weeks significantly depressed the serum zinc concentration and decreased body weight gain in the rats. These diets significantly increased the gastric secretory volume, acid and pepsin. Zinc deficiency produced or aggravated the formation of glandular ulceration in the absence or presence of stress, respectively; it also decreased the mast cell count in the gastric glandular mucosa. It is concluded that zinc deficiency adversely affects the rats by reducing the body weight gain and producing ulceration which is probably mast cell-mediated. On the other hand, it increases gastric secretory functions.

Effects of calcium channel blockers on gastric emptying and acid secretion of the rat in vivo

Experiments were designed to evaluate the effects of three calcium channel blockers (verapamil, diltiazem and cinnarizine) on gastric emptying and secretion in the rat. Pretreatment with the calcium blockers delayed gastric emptying of phenol red in a dose-dependent manner. Verapamil was the most effective of the agents tested. Verapamil and diltiazem inhibited gastric acid secretion in the pylorus-ligated rat without affecting pepsin output. Cinnarizine was ineffective in this model. When the perfused lumen of the anaesthetized rat was used, verapamil was found to inhibit responses to carbachol or histamine more than those to pentagastrin. Further, we found a greater sensitivity to verapamil for basal compared with vagal-stimulated (2-deoxy-D-glucose) acid secretion. Neither diltiazem nor cinnarizine modified gastric acid secretion in this experimental model. These findings are discussed in relation to the role of extracellular calcium in gastric motility and secretion, and the existence of a regional and functional selectivity for calcium blockers is proposed.