PURPOSE The aim of this study was to investigate in rats whether preoperative orogastric administration of low doses of cholera toxin would influence the mechanical strength of experimental colonic anastomosis on the basis of the gut mucosal immunomodulation effect of this antigen. METHODS: The cholera toxin group (n = 14) was fed 10 mug of cholera toxin in phosphate-buffered saline three times before surgery at 10-day intervals, whereas the controls (n = 14) received phosphate-buffered saline only. Twenty-four hours after the last close of cholera toxin (or placebo in control group), the animals underwent left colonic transection and anastomosis. Seven days after colonic transection-anastomosis, the bursting pressure of the anastomotic segment was recorded in situ. Perianastomotic and extra-anastomotic tissue samples were obtained for measurements of tissue transforming growth factor-beta, interleukin-6, and interferon-gamma levels with enzyme-linked immunosorbent assay. RESULTS: Cholera toxin administration resulted in a significantly higher bursting pressure than in the control group (165.78 +/- 12.37 vs. 138.4 +/- 7.87 mmHg; P < 0.001). Compared with the control group, the heightened mechanical strength of colonic anastomosis provided by cholera toxin was associated with significant increases in the perianastomotic tissue levels of transforming growth factor-beta (199.34 +/- 24.85 vs. 70.66 +/- 10.63 pg/ml; P < 0.001) and interleukin-6 (439.31 +/- 95. 14 vs. 289.57 +/- 96.59 pg/ml; P = 0.001), whereas interferon-gamma was significantly lower (174.04 +/- 44.82 vs. 219.00 +/- 31.35 pg/ml; P < 0.05). This cytokine pattern induced by cholera toxin in the wound milieu was also found to be similar in the extra-anastomotic colon, CONCLUSION: The mechanical strength Of uncomplicated experimental colonic anastomosis increased significantly with gut mucosal immunomodulation with repeated low preoperative doses of cholera toxin. This enhanced healing had significant positive correlation with the colonic tissue level of transforming growth factor-beta and inverse correlation with interferon-gamma. If the relevant dose regimen is identified and its safety is assured in humans, gut mucosal immunomodulation might provide an efficient, safe, and inexpensive toot to improve surgical outcome in colorectal surgery, particularly in high-risk situations.