Effects of CO insufflation into the colonic lumen on thiobarbituric acid (TBA)-reactive substances and tissue-associated myeloperoxidase (MPO) activity. The level of TBA-reactive substances (A) and MPO activity (B) were significantly inhibited in rats treated with CO gas insufflation. Data represent the mean ± SEM of 7 rats. *P < 0.05 relative to sham-operated rats. #P < 0.05 relative to rats with TNBS-induced colitis receiving normal air insufflation.