Saudi Journal of Gastroenterology
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Year : 1997  |  Volume : 3  |  Issue : 3  |  Page : 125-129
Selenium protects against ischemia-reperfusion­ induced gastric lesions in rats


1 Department of Medical Pharmacology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
2 Department of Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
3 Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia

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Date of Submission06-May-1997
Date of Acceptance02-Jul-1997
 

   Abstract 

Recent studies have shown that selenium afforded protection against ethanol and stress-induced gastric lesions in rats. The present study was undertaken to investigate the effect of selenium on ischemia-reperfusion-induced gastric injuries in which rats were subjected to 30 minutes of ischemia in the presence of 100 mM HCI and a reperfusion for 60 minutes duration. Intraluminal bleeding was assessed macroscopically and gastric lesions were graded microscopically under an inverted microscope. Nonprotein sulphydryl levels were measured spectrophotometrically. The severity of gastric lesions, intraluminal bleeding as well as the depletion of nonprotein sulphydryls during the reperfusion periods was significantly different from that of control. Pretreatment with selenium (0.125-2.0 mg/kg, intraperitoneally) 30 minutes before the ischemia-reperfusion, dose-dependently attenuated the gastric lesions, reduced the severity of intraluminal bleeding and prevented the depletion of nonprotein sulphydryls in the stomach. These results suggest that the gastric protection effect of selenium may be due to its antioxidant properties. Furthermore, endogenous nonprotein sulphydryls may play a significant role in the protective mechanisms of selenium.

How to cite this article:
Mobarok Ali AM, Al-Rashed RS, Al-Swayeh OA, Al-Humayyd MS, Mustafa AA, Al Tuwaijiri AS. Selenium protects against ischemia-reperfusion­ induced gastric lesions in rats . Saudi J Gastroenterol 1997;3:125-9

How to cite this URL:
Mobarok Ali AM, Al-Rashed RS, Al-Swayeh OA, Al-Humayyd MS, Mustafa AA, Al Tuwaijiri AS. Selenium protects against ischemia-reperfusion­ induced gastric lesions in rats . Saudi J Gastroenterol [serial online] 1997 [cited 2020 Oct 28];3:125-9. Available from: https://www.saudijgastro.com/text.asp?1997/3/3/125/33920


Ischemia in a stomach that contains acid has been shown to induce acute gastric lesions [1] . However, there is increasing evidence that much greater injuries to the gastric mucosa can occur during the reperfusion period following ischemia [2],[3],[4],[5],[6] . The gastric injuries induced by ischemia-reperfusion have been attributed to the liberation of oxygen­derived free radicals (ODFRs). Thus, it has been proposed that during ischemia, the high energy nucleotide adenosine triphosphate is metabolised to hypoxanthine and also the enzyme xanthine dehydrogenase is proteolytically converted to xanthine oxidase. On reperfusion, when oxygen is added, hypoxanthine forms the substrate for xanthine oxidase, which metabolises it to xanthine and uric acid, but also generates superoxide radical and hydrogen peroxide causing damage to gastric mucosa [7],[8] . Further evidence for the involvement of ODFRs in the pathogenesis of ischemia­reperfusion-induced gastric mucosal injuries comes from the studies that blocking the biochemical pathways through which ODFRs are generated or removing the radicals with various scavenging agents reduces the severity of gastric injuries. Thus, pretreatment with antioxidants such as allopurinol, superoxide dismutase, catalase, dimethylsulphoxide and α-tocopherol have been shown to attenuate ischemia-reperfusion-induced injuries [1],[3],[4],[6],[7],[8],[9],[10],[11] .

Antioxidant nutrients have recently received more attention from scientists in many disciplines because of their potential to prevent or delay the development of some chronic diseases [12],[13] . Selenium is an essential dietary trace element that has been shown to possess gastroprotective effects against experimentally-induced gastric lesions [14],[15] . Furthermore, it has been reported that one of the major physiological roles of selenium is to function as a general antioxidant [16],[17],[18] . Dietary selenium deficiency results in severe free-radical damage to tissues [18] . Selenium is an important constituent of antioxidant enzyme glutathione peroxidase [19],[20] . Therefore, this study was undertaken to investigate the effect of selenium on ischemia-reperfusion-induced gastric lesions in rats.


   Materials and methods Top


Drugs and chemicals used were obtained as indicated: sodium selenite (selenium, Fluka AG, Buchs, Switzerland), reduced glutathione, 5,5­dithio-bis-(2-nitrobenzoic acid) (DTNB), ethylenediaminetetraacetic acid (EDTA), and urethane were purchased from Sigma Chemical CO, Poole, England.

Male Wistar rats, weighing 220-250 gins, were obtained from the College of Medicine Animal Care Center, King Saud University, Riyadh, Saudi Arabia. They were maintained on standard rat chow diet but 24 hours before the start of the experiments they were deprived of food and kept in individual cages with raised mesh bottom to prevent coprophagia. The animals were allowed water ad libitum. All the studies were carried out on animals which were anesthetised with intraperitoneal (i.p.) injections of urethane (1.25 g/kg) and 6-10 animals were used for each group. The animals were killed whether anesthesia after the end of each experiment.

Retreatment of animals

Selenium (0.125 - 2.0 mg/kg, i.p.) was administered in a volume of 0.5 ml/100 g 30 minutes before the initiation of ischemia­reperfusion. Control groups received the same volume of distilled water by the i.p route.

Induction of ischemia-reperfusion

Ischemia-reperfusion-induced gastric lesions were produced as described by Andrews et al (5). Briefly, rats were anesthetised with urethane (1.25 g/kg, i.p). The stomach was exposed and the esophageal and pyloric ends of the stomach were occluded, using bull dog clamps. The celiac artery was identified, clamped and 100 mM HCL (1 ml/ 100 g) was introduced into the stomach with a syringe fitted with fine needle to maintain acid levels during ischemia. At 25 minutes of ischemia, the acid was withdrawn with a syringe fitted with fine needle, and the celiac artery clamp was removed after 30 minutes of ischemia. The tissue was then allowed to reperfuse for 60 minutes and the stomach was dissected out, examined macroscopically and scored for intraluminal bleeding as described previously (10,11). The gastric lesions were examined microscopically under an inverted microscope (Fluovert, Leitz, Germany) connected to a monitor (Sony, Japan) which is equiped with a measuring grid [11] . The extent of gastric mucosal lesions was assessed by an independent observer and expressed as mm 2 .

Measurement of nonprotein sulphydryls (NP-SH)

In separate experiments, following the same drug treatment schedules as described above, the gastric glandular NP-SH concentration was quantified according to the method of Sedlak and Lindsay [21] . The glandular part of the stomachs was cut, weighed, and homogenized in ice-cold 0.02 M EDTA. Five ml of the homogenates were mixed in a 15 ml test tutbe with 4 ml of distilled water and 1 ml of 50% trichloroacetic acid. The tubes were shaken intermittently for 15 minutes and centrifuged at 3000 g for 10 minutes. Two ml of supernatant were mixed with 4 ml of Tris-buffer (pH 8.9) and 0.1 ml DTNB was added and the sample was shaken. The absorbance was read within 5 minutes of addition of DTNB at 412 rim against a reagent blank (with no homogenates) in a spectrophotometer (Perkin­Elmer, Lamda 5). The final NP-SH concentration per gram of tissue was calculated from a previously constructed standard curve with reduced glutathione.


   Statistics Top


Results are expressed as the mean ± SEM. The significance of the differences in the mean values was calculated by Student's t-test for unpaired data. The level of statistical significance was taken as p<0.05.


   Results Top


Effect of selenium on ischemia-reperfusion-induced gastric lesions

Pretreatment of rats with selenium (0.125-2.0 mg/kg, i.p) dose-dependently reduced the gastric lesions and intraluminal bleeding induced by ischemia-reperfusion. Thus, at the highest dose used, there was about 77% attenuation of mucosal damage and complete protection of intraluminal bleeding scores. However, the values obtained with the lowest doses (0.125 and 0.25 mg/kg) used were not significantly different from controls [Table - 1].

Effect of selenium on gastric mucosal NP-SH levels

The gastric mucosal NP-SH content was significantly decreased following ischemia­reperfusion-induced injuries. Pretreatment of rats with selenium 30 minutes before the procedure inhibited the ischemia-reperfusion-induced depletion of mucosal NP-SH levels [Table - 2].


   Discussion Top


The present investigation demonstrates that selenium, an essential trace element, prevents ischemia-reperfusion-induced gastric mucosal lesions, intraluminal bleeding and depletion of NP­SH levels in the rat stomach.

The cellular damage caused by gastric ischemia­reperfusion is considered to be due to ODFRs' reaction processes and endogenous antioxidants play an important role to protect tissues from oxidative stress [7],[8] . However, excessive genertion of ODFRs may overwhelm the endogenous defense system and administration of exogenous antioxidants has been shown to afford protection [1],[3],[4],[6],[7],[8],[9],[10],[11] . The ability of selenium to reduce the severity of ischemia-reperfusion-induced gastric injuries may suggest an antioxidant effect of selenium on this test system. These findings are consistent with the previous reports that showed selenium is able to attenuate ethanol and stress­induced gastric lesions [14],[15] in which ODFRs are suggested to play a significant role [22],[23],[24],[25] .

Further supporting evidence for an antioxidant mechanism of selenium in the present study may be explained by its ability to prevent ischemia-­reperfusion-induced depletion of NP-SH in the stomach. Nonprotein sulphydryl (mainly reduced glutathione) is an important constituent of the intracellular protective mechanisms against a number of stimuli including oxidative stress [26],[27] . The maintenance of a critical level of endogenous gastric NP-SH level has been suggested to be important for the gastric mucosa to resist damge when challenged with noxious stimuli. Reduction of tissue glutathione to less than 30% of normal values has been found to be associated with increased toxicity to electrophilic substances [28] . Moreover, sulphydryl compounds have the ability to bind reactive free radicals produced in tissues following exposure to cytotoxic compounds [26],[27] . Thus, the restoration of gastric NP-SH levels after pretreatment with selenium may be due to inhibition of generation as well as removal of ODFRs and thus sparing consumption of NP-SH by the generated ODFRs. Reduced glutathione is a known substrate for the enzyme glutathione peroxidase. Selenium may discharge its duty by being required for the synthesis and enzymatic activity of selenium­dependent glutathione peroxidases and selenium­dependent phospholipid hydroperoxide glutathione peroxidases which are responsible for removal of hydrogen peroxide and destruction of phospholipid hydroperoxides, respectively [19],[20] . The present findings may suggest that endogenous NP-SH may be involved in the protective mechanisn of selenium. This is consistent with a previous report which has shown that ischemia-reperfusion-induced liver injuries are associated with depletion of NP-SH level in the hepatocytes and treatment with the antioxidant, allopurinol reverses this depletion and affords protection [29] .

In conclusion, the results of the present study indicate that selenium attenuates ischemia-­reperfusion-induced gastric lesions, intraluminal bleeding and prevents depletion of NP-SH levels in rats. It is suggested that this gastric protection effect of selenium may be, at least in part, due to its antioxidant properties.

 
   References Top

1.Perry MA, Wadhwa S, Parks DA, Pickard W, Granger DN. Role of oxygen radicals in ischemia-induced lesions in the cat stomach. Gastroenterol 1986;90:362-7.  Back to cited text no. 1    
2.Perry MA, Wadhwa S. Gradual reintroduction of oxygen reduces reperfusion injury in cat stomach. Am J Physiol 1988;254:6366-72.  Back to cited text no. 2    
3.Yoshikawa T, Yasuda M, Ueda S et al. Vitamin E in gastric mucosal injury induced by ischemia-reperfusion. Am J Clin Nutr 1991;53:21OS-4.  Back to cited text no. 3    
4.Andrews FJ, Malcontenti-Wilson C, O'Brien PE. Sequence of gastric mucosal injury following ischemia and reperfusion: The role of reactive oxygen metabolites. Dig Dis Sci 1992;37:1356-61.  Back to cited text no. 4    
5.Andrews FJ, Malcontenti-Wilson C, O'Brien PE. Protection against gastric ischemia-reperfusion injury by nitric oxide generators. Dig Dis Sci 1994;39:366-73.  Back to cited text no. 5  [PUBMED]  
6.Ali ATMM, Al-Swayeh OA, Al-Rashed RS, Al-Mofleh IA, Al-Dhohayan AD, Al Tuwaijiri AS. Role of oxygen-derived free radicals on gastric mucosal injury induced by ischemia­-reperfusion. Saudi J Gastroenterol 1996;2:19-28.  Back to cited text no. 6    
7.Koningsberger JC, Mark JJM, Vanttattum J. Free radicals in gastroenterology. Scand J Gastroenterol 1988;23(suppl 154):30-40.  Back to cited text no. 7    
8.Parks DA. Oxygen radicals: Mediators of gastrointestinal pathophysiology. Gut 1989;30:293-8.  Back to cited text no. 8  [PUBMED]  [FULLTEXT]
9.Halliwel B. Drug antioxidant effects. A basis for drug selection. Drugs 1991;42:569-605.  Back to cited text no. 9    
10.Al-Tuwaijri AS, Al-Dhohayn AD. Protective effects of a­tocopherol on gastric mucosal injury by ischemia-reperfusion in rats. Med Sci Res 1995;23:627-8.  Back to cited text no. 10    
11.Al-Dohayan AD, Al-Tuwaijri AS. The potential synergistic effect of calcium channel blockers and a-tocopherol on gastric mucosal injury induced by ischemia-reperfusion. Eur J Gastroenterol Hepatol 1996;8:1-4.  Back to cited text no. 11    
12.Machlin U, Bendich A. Free radical tissue damage: Protective role of antioxidant nutrients. FASEB J 1987; 1:441-5.  Back to cited text no. 12    
13.Diplock AT. Antioxidant nutrients and disease prevention: An overview. Am J Clin Nutr 1991;53:1895-1935.  Back to cited text no. 13    
14.Parmer NS, Tariq M, Ageel AM. Gastric anti-ulcer and cytoprotective effect of selenium in rats. Toxicol Appl Pharmacol 1988:91;122-30.  Back to cited text no. 14    
15.Al-Moutairy AR, Tariq M. Effect of vitamin E and selenium on hypothermic restraint stress and chemically-induced ulcers. Dig Dis Sci 1996;41:1165-71.  Back to cited text no. 15  [PUBMED]  
16.Burk RF. Recent developments in trace element metabolism and function: Newer roles of selenium in nutrition. J Nutr 1989;119:1051-4.  Back to cited text no. 16  [PUBMED]  [FULLTEXT]
17.Burk RF. Protection against free radical injury by selenoenzymes. Pharmoacol Ther I990;45:383-5.  Back to cited text no. 17    
18.Bettger WJ. Zinc and selenium, site-specific versus general antioxidation. Can J Physiol Pharmacol 1993;71:721-4.  Back to cited text no. 18  [PUBMED]  
19.Hoekstra WG. Biochemical function of selenium and its relation to vitamin E. Fed Proc 1975;34:2083-9.  Back to cited text no. 19  [PUBMED]  
20.Maiorino M, Chu FF, Ursini F, Davies K, Doroshow JH, Esworthy RS. Phospholipid hydroperoxide glutathione peroxidase is the 18 kDa selenoprotein expressed in human tumor cell lines. J Biol Chem 1991;266:7728-32.  Back to cited text no. 20    
21.Sedlak J, Lindsay RH. Estimation of total, protein-bound, and nonprotein sulphydryl groups in tissue with Ellman's reagent. Anal Biochem 1968;25:192-205.  Back to cited text no. 21  [PUBMED]  
22.Szelenyi I, Brune K. Possible role of oxygen free radicals in ethanol-induced gastric mucosal damage in rats. Dig Dis Sci 1988;33:865-71.  Back to cited text no. 22  [PUBMED]  
23.Ligumsky M, Sestieri M, Okon E, Ginsberg 1. Antioxidants inhibit ethanol-induced gastric injury in the rat. Scand J Gastroenterol 1995;30:854-60.  Back to cited text no. 23    
24.Cochran T, Stefanko J, Moore C, Saik R. Dimethylsulfoxide protection against gastric stress ulceration. Current Surg 1983;40:435-7.  Back to cited text no. 24    
25.Inoue M, Hirota M, Ando Y, Akagi M, Morinoy Y. Role of reactive oxygen species in the pathogenesis of stress-induced gastric mucosal lesions. In: Tsuchuya M, Kondo M, Yoshikawa T, eds. Free radicals in Digestive Disease 1988; Amsterdam; Elsevier, pp 93-98.  Back to cited text no. 25    
26.Kosower NS, Kosower EM. The glutathione status of the cell. Int Rev Cytol 1978;54:109-60.  Back to cited text no. 26  [PUBMED]  
27.Olson CE. Glutathione modulates toxic oxygen metabolite injury of canine chief cell monolayer in primary culture. Am J Physiol 1988;254:G49-G56.  Back to cited text no. 27  [PUBMED]  [FULLTEXT]
28.Babson JR, Abell NS, Reed DJ. Protective role of glutathione redox cycle against adriamycin-induced toxicity in isolated hepatocytes. Biochem Pharmacol 1981;30:2299-304.  Back to cited text no. 28  [PUBMED]  [FULLTEXT]
29.Karwinski W, Uivik R, Farstad M, Avardal A, Berge R, Soreide O. Effect of allopurinol on the concentration of endogenous glutathione in hepatocytes after an hour of normothermic liver ischemia. Eur J Surg 1993;159:355-9.  Back to cited text no. 29    

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Correspondence Address:
Abu Taib Mohammed Mobarok Ali
Department of Medical Pharmacology (31), College of Medicine, King Saud University, P.O. Box 2925, Riyadh 11461
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


PMID: 19864789

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