4.9.8 Gastrointestinal Disease Models
Gastrointestinal disease models evaluate candidate antiulcer, gastroprotective, and anti-inflammatory bowel disease agents using endpoints ranging from...
Gastrointestinal disease models evaluate candidate antiulcer, gastroprotective, and anti-inflammatory bowel disease agents using endpoints ranging from macroscopic mucosal lesion scoring to detailed histopathological and biochemical inflammatory marker assessment.
Gastric Ulcer — Ethanol- and Pylorus Ligation-Induced Models
Peptic ulcer disease is modelled using complementary acute injury protocols targeting distinct components of gastric mucosal defence. The ethanol-induced ulcer model exploits the direct necrotising effect of absolute or concentrated ethanol on the gastric mucosa, administered orally to fasted rats, producing macroscopically visible haemorrhagic mucosal lesions within one hour that are quantified using an ulcer index derived from lesion number and length. The pylorus ligation (Shay rat) model instead surgically ligates the pylorus, causing accumulation of gastric acid and pepsin within the stomach over several hours, allowing direct measurement of gastric secretory parameters (volume, free and total acidity, and pepsin activity) alongside mucosal lesion scoring, and is therefore particularly suited to evaluating antisecretory (as opposed to purely cytoprotective) mechanisms. Standard reference comparators include proton-pump inhibitors (omeprazole) for antisecretory evaluation and sucralfate or misoprostol for mucosal-protective evaluation. Together, these complementary models allow a candidate compound's gastroprotective mechanism — whether antisecretory, mucus-stimulating, or antioxidant — to be dissected.
Ulcerative Colitis — DSS- and TNBS-Induced Models
Inflammatory bowel disease is modelled using two chemically distinct colitis-induction protocols. Administration of dextran sulphate sodium (DSS) in the drinking water (typically 2–5% w/v for five to seven days) disrupts the intestinal epithelial barrier directly, producing a colitis phenotype — weight loss, diarrhoea, rectal bleeding, and colonic shortening — that is particularly useful for studying epithelial barrier dysfunction and innate immune mechanisms, and closely models human ulcerative colitis. Intrarectal instillation of 2,4,6-trinitrobenzene sulphonic acid (TNBS), dissolved in ethanol to permeabilise the mucosa, instead produces a hapten-driven, T-cell-mediated transmural colitis more closely resembling Crohn's disease. Both models are assessed using the Disease Activity Index (a composite clinical score incorporating weight loss, stool consistency, and rectal bleeding), colon length (an inverse marker of inflammatory severity), histopathological colitis scoring, and inflammatory cytokine profiling (TNF-alpha, IL-6, IL-1beta) in colonic tissue. 5-Aminosalicylates (sulfasalazine, mesalamine) and corticosteroids serve as standard reference comparators, reflecting first-line human inflammatory bowel disease therapy.