Ulcerative colitis (UC) is a chronic inflammatory disease, characterized by colon surface mucus layer damage. UC if usually followed by the development of continuous hemorrhagic inflammation in colon, which does occur in rectum and spreads in proximal direction. The development of inflammatory processes in colon initiates after the impairment of intestine barrier integrity. As a result of neutrophil recruiting activation and the development of inflammatory processes the increase of epithelial barrier permeability for bacteria was observed. It was previously shown that alterations in mucus barrier structure is among early factors of early UC development. It was previously reported that the sulphatation level of mucus mucins in patients with UC were decreased; the mucus mucins are essential for maintaining of normal colon physiological functioning. The aim of this study was to investigate dynamic changes in total glycoprotein level and its carbohydrate composition at differents terms during UC in rats. The study was performed on male Wistar rats (160–180 g, n = 24). UC was induced by 6 % iodoacetamide (IA) injection, dissolved in 1 % methylcellulose (0.1 ml, per rectum). Control rats received 1 % methylcellulose solution (0.1 ml, per rectum). Animals were subjected to an autopsy in 0.5, 2, 6 hours and on the 3rd and 7th day of experiment. Total level of mucus glycoproteins, hexoses, hexosamines, fucose and sialic acids in colon mucus were measured. It was determined that total glycoprotein level significantly increased starting from 6 hr after IA enema (1.7-fold, р < 0,05), which remained unchanged on the 3rd (2-fold increase, р < 0,05) and 7th (1.8-fold increase, р < 0,05) days of experiment vs. control group. These changes were accompanied by the increase of hexose content on the 3rd (7.7-fold, р < 0,05) and 7th (5.5-fold, р < 0,05) days of experiment vs. control group. At the same time the fucose level was sharply decreased in 6 hr (3.3-fold, р < 0,05) and on the 3rd (4-fold, р < 0,05) and 7th (7.5-fold, р < 0,05) days of experimen vs. control group. The hexoasmine level was incresed in 0.5 (2.4-fold, р < 0,05), 2 (2.4-fold, р < 0,05), 6 hr (2.9-fold, р < 0,05) and on the 3rd (3.2-fold, р < 0,05) and 7th (3.9-fold, р < 0,05) days of experiment vs. control group. The sialic acid level was increased in 6 hr (1.4-fold, р < 0,05) and on the 3rd (1.3-fold, р < 0,05), 7th (1.7- fold, р < 0,05) days of experiment vs. control group. The increase of total glycoprotein level was accompanied by sharp decrease of fucose content and increase of sialic acids content in mucin carbohydrate composition. This indicates about secretion process activation of mucins, which have less ramified carbohydrate part. Although, despite taking into account the increase of total mucin amount and elongation of carbohydrate chains by the increase of hexose level, this mucus is less tight and might be hardly held on the epithelial cells surface due to the low state of ramifidation. Moreover, the decrease of the amount of glycoprotein side carbohydrate chains might lead to the increase of the epithelium susceptibility to microorganisms and foreign macromolecules, which, in its turn, support the inflammatory process in colon. The slowly progressing changes of total glycoprotein level and carbohydrate composition in surface colon mucus layer were observed during experimental colitis in rats. These changes were manifested through the increase in total glycoprotein, hexose, hexosamine, sialic acid levels while the fucose level was decreased. This might indicate about the impairment of surface colon mucus layer function during the chronic stage of UC.
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