Abstract: AIM: To investigate the effect and mech-anism of 5-aminosalicylic acid (5-ASA) in topical treat-ment on trinitrobenzene sulfonic acid (TNBS)-induced co-litis in rats.METHODS: Colitis wasinduced by intraco-lonic administration of TNBS and was treated with 5-ASA at the dose of 100 mg·kg^-1 for2 weeks.Normal control grouPwas administrated with normal saline and TNBS control grouPwas treated with TNBS,not with 5-ASA.Macroscopic damage,histological changes and myeloper-oxidase (MPO) activity were evaluated.Superoxide dis-mutase (SOD) activity and malondialdehyde (MDA) level in colonic mucosa were detected by kits.The expression of interleukin-1β(IL-1β) and tumornecrosis factor-α(TNF-α) mRNAs in colonic mucosa was determined by a reverse transcription and polymerase chain reaction meth-od.RESULTS: Compared with TNBS control group,the macroscopic and histological changes and MPO activity in 5-ASA treated groups were improved.SOD activity was increased and the level of MDA in colonic mucosa was re-duced significantly.The expression of IL-1βand TNF-mRNAs in colonic mucosa was also decreased significant-ly.CONCLUSION: 5-ASA enema can significantly ameliorate TNBS-induced colitis in rats via antioxidant mechanism and attenuation of proinflammatory cytokine expression.

Key words: 5-aminosalicylic acid, TNBS induced colitis, superoxide dismutase, malondialdehyde, interleu-kin-1β, tumornecrosis factor-α