RESUMO
To develop and validate methods for the assessment of colonic damage in the rat that are rapid, simple to perform and quantitative. Rats [Sprague Dawley, male, N = 52] were administered 0.5 mL of 2,4,6-trinitrobenzenesulfonic acid [TNBS, 60 mg mL -1 in 50% ethanol] intracolonically to induce reproducible experimental colitis. The rats were administered either orally or intracolonically 1 g of the non-absorbable permeability marker phenol red in 0.5 mL of water 24-72 h post-colitis induction. Urine was collected for the next 24 h and analyzed for phenol red at 559 nm using a spectrophotometer. In separate studies, colonic tissue was excised 24-72 h post-colitis induction for mitochondrial DNA damage determination. Baseline permeability indicated that < 4% of phenol red dose was excreted in urine after oral or intracolonic administration to vehicle control rats. A 3-4 fold increase in colonic permeability was apparent in colitic rats 48 h post TNBS, which correlated with gross macroscopic ulceration in the large bowel and colonic mitochondrial damage. Administration of dexamethasone 2 mg kg -1, or 5-aminosalicylic acid [5-ASA] 100 mg kg -1 resulted in significant gross macroscopic protection and reduction of colonic permeability and mitochondrial damage. In a group of rats TNBS was administered and then allowed to recover for 6 weeks. Subsequent tail vein administration of TNBS 5 mg kg -1 for 3 days reactivated the disease, which was also detected by an increase in colonic permeability of phenol red and oxidative mitochondrial damage. Several non-steroidal anti-inflammatory drugs administered in this model also appeared to exacerbate this disease and increase colonic permeability and mitochondrial damage. Oral or rectal administration of phenol red in experimental colitis can reproducibly detect colonic damage. This marker can also be used to non-invasively evaluate potential treatments for experimental colitis as well as its reactivation. Mitochondrial damage to colonic tissue parallels the increase in colonic permeability and appears to be a sensitive marker of disease activity in experimental colitis