['Inflammatory bowel diseases are accompanied by alterations in the contractile function of colonic muscle. Whether these changes are also accompanied by the production of interleukin-1 beta (IL-1 beta) mRNA remains unknown.', 'To investigate the profile of IL-1 beta mRNA in the colonic muscle of rats with acetic acid induced colitis.', 'Colitis was induced by intrarectal administration of 1 ml of 4% acetic acid 8 cm from anal margin. Myeloperoxidase activity was used as a marker of inflammation in the colon. RNA was extracted from colonic muscle and was used to amplify the level of IL-1 beta mRNA with a reverse transcription coupled polymerase chain reaction (RT-PCR) method developed in this study.', 'Colonic muscle exhibited constitutive expression of IL-1 beta mRNA. The level was enhanced significantly, one, two, and five days after acetic acid administration. On day 7 after treatment, the level of IL-1 beta mRNA had returned baseline values. This profile of IL-1 beta mRNA was consistent with myeloperoxidase activity.'] Does colonic muscle enhance the production of interleukin-1 beta messenger RNA in experimental colitis?