Association between permeability of the colonic wall and azoxymethane induced cancer of the colon in rats.

OBJECTIVE: To investigate the association between colonic permeability and the development of azoxymethane induced colonic cancer in rats. MATERIAL: Seventy-three male Fischer-Cooper hybrid rats. INTERVENTIONS: Measurement of the concentrations of sodium fluorescein in plasma as an indication of its passage across the bowel wall in control rats, and six weeks and six months after injection of azoxymethane. RESULTS: Forty-seven rats were given azoxymethane, and 26 acted as controls. Sodium fluorescein was instilled into segments of right (n = 46) and left (n = 27) colon and measured in peripheral blood; significantly higher concentrations were recorded after instillation into the left than into the right colon. No tumours developed in the 15 rats that were given azoxymethane and were examined after six weeks. At six months, however, 29 of the remaining 32 had developed 94 macroscopic tumours (range 1-12 tumours/rat), and 89 of these (95%) were in the left colon. CONCLUSION: The greater permeability of the left colon in rats compared with the right may be associated with the higher incidence of carcinomas in the left compared with the right colon.