THE EFFECTS OF CHRONIC EXPOSURE TO CHROMIUM SALTS ON GASTRIC ULCERATION IN MALE WISTAR RATS

Abstract

The gastrointestinal tract is constantly exposed to various protective and aggressive factors from food. Recent studies have shown that factors, including heavy metal exposure and diet may alter gastrointestinal mucosal integrity. Chromium (Cr), a naturally occurring polyvalent element found in rocks, soil and gases is known to be present in whole grains, wheat, cereal, lettuce, onions, potatoes, green beans, raw tomatoes and many other food items. The role of Cr in gastrointestinal mucosa protection or erosion is not well studied. In this study, the effects of exposure to tri-and hexavalent Cr on gastric ulcer were investigated in rats. Sixty male Wistar rats (100-120g) were randomly assigned to six groups of 10 animals each. Four groups were treated with Cr; Chromium III-10ppm (CrIII-10), Chromium III-100 ppm (CrIII-100), Chromium VI-10ppm (CrVI-10) and Chromium VI-100pm (CrVI-100) while the remaining two groups were non-ulcerated control (nCont) and ulcerated control (uCont). Twelve weeks after Cr administration, experimental gastric ulcers were induced via pylorus ligation (PL) technique (a=5 per group). In the remaining five animals, ulcer was induced by oral administration of indomethacin (40mg/kg). In both ulcer models, animals were sacrificed four hours after ulcer induction. Blood and stomach biopsies were collected and analysed. Ulcer was assessed based on macroscopic appearance of the stomach using standard ulcer score scale. Lipid peroxidation, catalase and Superoxide Dismutase (SOD) activities of the stomach homogenates were assessed by spectrophotometry. Histology of the stomach tissues were assessed to determine the degree of tissue damage using microscopy. Blood were subjected to descriptive statistics and analysed using ANOVA at α>0.05. The blood Cr level was significantly increased in the Cr treated groups (CrIII-10: 0.12±0.01 ppm; CrIII-100: 0.12±0.01 ppm; CrVI-10: 0.13±0.01 ppm and CrVI-100:0.12±0.03 ppm) compared with nCont (0.08±0.01 ppm). Ulcer scores were nCont (0.0±0.0; 0.0±0.0), uCont (4.0±0.5; 12.6±0.5), CrIII-10 (1.6±0.2 ; 10.3±0.5), CrIII-100 (2.8±0.1; 10.8±0.2), CrVI-10 (1.8±0.3, 11.4±0.5) and CrVI-100 (2.8±0.3; 12.1±0.5) for PL and indomethacin, respectively. Various degrees of gastric protection were observed in the two ulcer models on exposure to CrIII-10(59.4%, 18.7%), CrIII-100 (31.3%; 14.5%), CrVI-10 (56.3%; 9.7%) and CrVI-100 (31.3%; 4.0%). There were significant decreases in gastric acidity in Cr- treated groups (CrIII-10:12.0±1.0; CrIII-100: 26.9±2.3 mEq/L/100g: CrVI-10: 16.0±1.5: CrVI-100: 26.8 ±1.5 mEq/L/100g) compared with uCont (34.0±1.0 mEq/L/100g) for PL model. Lipid peroxidation levels in both PL and indomethacin ulcer models were significantly in uCont (11.9±0.1; 6.3±0.1 nmol/mg) than Cr- treated groups (CrIII-10: 8.2±0.1; 4.9±0.0; 4.9±0.0; CrIII-100: 9.0±0.3: 5.3±0.1 nmol/mg; CrVI-10: 8.9±0.3: 5.6±0.0: CrVI-100: 9.7±0.2: 6.0±0.0 nmol/mg). The activities of SOD and catalase were elevated in Cr-treated groups of both ulcer models relative to uCont. Ulcer score results were further corroborated by histological evaluation which revealed mild erosion of surface epithelium in the Cr-treated groups against visible lesions in uCont. Both tri and hexavalent Chromium offers protection against gastric ulcer induced by pylorus ligation and indomathacin via reduction of gastric oxidative stress.