Does increased gastric mucus play a role in the ulcer-protecting effects of zinc sulphate?

Interaction and competition for intestinal absorption by zinc, iron, copper, and manganese at the intestinal mucus layer

Trace elements such as zinc, manganese, copper, or iron are essential for a wide range of physiological functions. It is therefore crucial to ensure an adequate supply of these elements to the body. Many previous investigations have dealt with the role of transport proteins, in particular their selectivity for, and competition between, different ions. Another so far less well investigated major factor influencing the absorption of trace elements seems to be the intestinal mucus layer. This gel-like substance covers the entire gastrointestinal tract and its physiochemical properties can be mainly assigned to the glycoproteins it contains, so-called mucins. Interaction with mucins has already been demonstrated for some metals. However, knowledge about the impact on the respective bioavailability and competition between those metals is still sketchy. This review therefore aims to summarize the findings and knowledge gaps about potential effects regarding the interaction between gastrointestinal mucins and the trace elements iron, zinc, manganese, and copper. Mucins play an indispensable role in the absorption of these trace elements in the neutral to slightly alkaline environment of the intestine, by keeping them in a soluble form that can be absorbed by enterocytes. Furthermore, the studies so far indicate that the competition between these trace elements for uptake already starts at the intestinal mucus layer, yet further research is required to completely understand this interaction.

The role of zinc sulfate and metallothionein in protection against ethanol-induced gastric damage in rats

In this study, the effects of zinc sulfate against ethanol-induced acute gastric damage in rats were investigated, morphologically and biochemically. In addition, the present investigation has demonstrated the distribution of metallothionein stimulated by zinc in gastric mucosal tissues, immunohistochemically. The gastric damage was induced by intragastric administration of 1 ml absolute ethanol per rat. Rats received zinc sulfate (100 mg/kg/day) for 3 consecutive days 2 hr prior to the administration of absolute ethanol. Acute ethanol exposure caused degenerative morphological changes, a decrease in metallothionein immunreactivity; an increase in lipid peroxidation (LPO) levels, and a decrease in reduced glutathione (GSH) levels in gastric mucosa. On the other hand, zinc sulfate administration to ethanol-treated rats caused a significant reduction in the histological damage, an increase in metallothionein immunreactivity, a decrease in LPO levels, and an increase in GSH levels in gastric mucosa. As a result, the present study indicates that zinc sulfate has a protective effect against ethanol-induced acute gastric damage. In addition, we might say that the zinc given as exogenous protection against acute gastric damage has a protective effect both by stimulation of metallothionein synthesis and through GSH as well as having antioxidative potential.

Attenuation of indomethacin- and HCl/ethanol-induced oxidative gastric mucosa damage in rats by kolaviron, a natural biflavonoid of Garcinia kola seed

Reactive oxygen species (ROS) have been implicated in the aetiology of HCl/ethanol- and indomethacin gastric mucosal damage. This study investigated the protective effects of kolaviron, a natural antioxidant from the seed of Garcinia kola, on oxidative gastric mucosal damage induced by HCl/ethanol, and indomethacin.A HCl/ethanol mixture (1.5 mL of 0.15 n HCl in 70% ethanol) and indomethacin (IND) caused severe gastric damage with an ulcer index of 2.90 +/- 0.8 and 2.5 +/- 0.4, respectively, and significant reductions in the gastric mucosal content of catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) (p < 0.001).Pre-treatment of animals with kolaviron (100 mg/kg) orally 1 h and once daily for 3 days prior to ulcer induction significantly reduced the formation of ulcers induced by HCl/ethanol with preventive ratios of 65 and 72, respectively, while rats treated with kolaviron 1 day and for 7 days prior to IND treatment attenuated ulcer formation by 59% and 77%. Pre-treatment with ranitidine 1 h prior to ulcer induction (50 mg/kg) elicited preventive ulcer ratio of 55. Kolaviron pre-treatment 1 h before ulcer induction attenuated the HCl/ethanol reduction in CAT, SOD and GSH by 43%, 42% and 30%, respectively, and 67%, 68% and 64% following 72 h treatment with kolaviron. Ranitidine elicited 24%, 41% and 29% protective effects, respectively.Similarly, kolaviron administered to rats 1 day and for 7 days before IND treatment attenuated the drug-induced inhibition of CAT by 44% and 70%; SOD by 23% and 43% and GSH by 32% and 55%, respectively. In a 1 h and 3-day treatment with kolaviron before HCl/ethanol administration, MDA was reduced by 35% and 55%, respectively, while kolaviron administration 1 day and for 7 days before IND elicited a 39% and 58% reduction in MDA. Ranitidine elicited 39% and 50% reduction in MDA following HCl/ethanol and IND treatment. The results indicate the gastroprotective activity of kolaviron, which may be linked to its intrinsic antioxidant properties.

Tungstic acid reduction of cold-resistant stress-induced ulceration in rats

Sprague-Dawley rats were restrained at 4 degrees C for 2 h (stress). Tungstic acid in a single dose of 0.01, 0.1, 1, 10, 100 or 300 mg/kg (dissolved in distilled water) was administered intragastrically to animals 30 min prior to stress. Stress induced significant gastric mucosal damage, whereas tungstic acid pretreatment dose-dependently reduced lesion formation. Doses of tungstic acid of 1 mg/kg and higher significantly (P < 0.05-0.001) decreased ulcers. The mucosal mast cell counts in rats pretreated with tungstic acid were significantly higher than those of control rats. In motility experiments using oral administration of amberlite pellets, pretreatment with tungstic acid dose-dependently reduced the gastric emptying rate during a 1 h period of stress. Gastric mucosal xanthine oxidase and superoxide dismutase (SOD) activities, after pretreatment with a single dose of tungstic acid, were not altered in stressed animals. It is suggested that tungstic acid effectively antagonizes stress-induced gastric ulcers, possibly by decreasing motility and mass cell degranulation. Xanthine oxidase and SOD activities and mucous content were not changed in the gastric mucosa by the present method of tungstic acid administration.

Chronic nicotine treatment intensifies gastric ulceration by cold-restraint stress in rats

Nicotine 5, 25 or 50 micrograms/ml drinking water given ad lib for 5, 10 or 20 days, dose- and time-dependently worsened cold-restraint-induced (stress) ulceration in rat stomachs. Treatment with nicotine 5 or 25 micrograms/ml did not influence the number of gastric mucosal mast cells degranulated by cold and restraint; however, drinking 50 micrograms/ml for 10 days lowered further the mast cell count in stressed animals. During 20-day nicotine administration, the daily food intake and body weight gain, up to the 18th day when the animals were starved before experiments, were not affected by the three concentrations of the alkaloid, except that fluid consumption tended to be less only in those animals given the highest dose. The findings indicate that chronic nicotine treatment exacerbates the severity of stress-evoked ulcer formation. The ulcer-intensifying mechanism of the two lower doses of nicotine appears not to be related to additional mast cell degranulation; only the ulcerogenic action of the highest concentration includes this factor. It is unlikely that ulcer aggravation by nicotine is due to malnutrition because body weight gain and solid food intake by the alkaloid-treated rats were normal.

Effect of zinc sulphate on acetic acid-induced gastric ulceration in rats

The effects of zinc sulphate on gastric ulcer healing rate and mucosal mucus content of acetic acid-induced ulceration in rats have been assessed. Daily treatment with zinc sulphate progressively accelerated ulcer healing in a dose-dependent manner with a significant increase observed on day 15 after ulcer induction in rats treated with 44 and 88 mg kg-1 zinc sulphate. A significant increase in gastric mucosal adherent mucus was also observed in those animals treated with 88 mg kg-1 zinc sulphate. The results suggest that a minimum treatment period of 15 days is needed for the zinc sulphate to be effective, and that zinc ions may promote gastric ulcer healing by enhancing mucus formation to prevent acid back-diffusion into the gastric mucosa.

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.

The antiulcer effect of verapamil in relation to gastric calcium levels in stressed rats

The antiulcer effect of verapamil, and its relationship to stomach calcium levels, were examined in rats restrained at 4 degrees C (stress). Stress for 2 hr significantly increased muscle calcium and induced mucosal ulceration in the gastric glandular segment; calcium concentrations in the glandular mucosa and serum were unaffected. Verapamil or calcium gluconate given 30 min before stress prevented the rise in gastric muscle calcium, and attenuated ulcer severity. Bis(beta-aminoethylether)-NNN'N'-tetra-acetic acid (EGTA) pretreatment, however, further elevated stomach muscle calcium and markedly worsened lesion formation. These findings suggest that increased stomach muscle calcium could be a causal factor in stress-induced gastric glandular ulceration.

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.

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.

Luminal acid in stress ulceration and the antiulcer action of verapamil in rat stomachs

The role of luminal acid and the influence of the antisecretory action of verapamil in stress ulcer prevention in rat stomachs have been studied. Intraperitoneally injected verapamil, 4 mg kg-1, inhibited gastric acid secretion and ulcer formation, however, a 2 mg kg-1 dose, which did not significantly influence acid output, also had an antiulcer effect. Intraperitoneal injection of bethanechol, 1.2 or 3.6 mg kg-1, increased gastric acid output, but did not influence stress-induced ulcer formation. Oral administration of HCl, 25 or 50 mu equiv, aggravated stress ulceration in a dose-dependent manner; this lesion-worsening effect was prevented by pretreatment with verapamil or bethanechol. The gastric luminal acid content in 2 h pylorus-ligated rats was similar in the groups given either bethanechol or HCl. These findings indicate that the antisecretory action of verapamil may not account for its antiulcer effect. It is suggested that endogenous and exogenous luminal acid may have different influences on stress ulcer formation.

Nutritional modulation of mineralocorticoid and prostaglandin production: potential role in prevention and treatment of gastric pathology

Various lines of evidence indicate that aldosterone and prostaglandins may play physiological roles in protecting the gastric mucosa. This would suggest that low-sodium, high-potassium diets, and supplementation with essential fatty acids that are efficient prostaglandin precursors (as in evening primrose oil), may have value in the prevention and treatment of gastric ulcer and gastritis. A low-sodium, high-potassium diet may also reduce the risk of gastric cancer.

The role of zinc ion in the development of gastric ulcers in rats

The properties of the gastric mucosal barrier and acid output were investigated in zinc deficient rats. A decline in total acid output, a significant diminution in hydrogen and sodium ion fluxes and an increase in gastric lesions suggest a marked breakdown of the gastric mucosal barrier in zinc deficient rats.

Reserpine-induced gastric ulcers: protection by lysosomal stabilization due to zinc

The effects of graded doses of zinc sulfate pretreatment on reserpine-induced gastric ulceration and on lysosomal fragility both in vivo and in vitro, were studied in rats. Reserpine treatment (5 mg/kg, i.p., 18 h before sacrifice) induced marked gastric glandular ulceration and elicited the release of free beta-glucuronidase from lysosomes in the gastric mucosa. A similar effect on release of this enzyme from isolated rat hepatic lysosomes was observed after in vitro incubation with reserpine. Zinc sulfate (22, 44 or 88 mg/kg, i.p., 30 h before reserpinization, or 10(-3) M in vitro) inhibited the reserpine-induced response, and zinc sulfate alone (10(-11)--10(-3) M) also stabilized lysosomal membrane permeability to beta-glucuronidase. No direct effect of zinc or reserpine on purified beta-glucuronidase activity was observed. In conclusion, it is postulated that the stabilizing effect of zinc on lysosomal membranes, as manifest by reduced release of beta-glucuronidase from isolated lysosomes, is one of the protective mechanisms of zinc against reserpine-induced ulceration.