New experimental model of proximal and distal colon transposition in rats

The proximal and distal portions of the colon have different morphologic and histochemical features. To ascertain whether these features are genetically or environmentally determined, we attempted to develop a transposition model of the proximal and distal portions of the colon in rats. Four-month-old male Fisher 344 rats were used. Four centimeters of the proximal colon segment circulated by the right colonic artery and 4 cm of the distal colon segment circulated by the middle colic artery were interchanged isoperistaltically. In the control group, the colon was transected and reanastomosed. All rats tolerated the surgery and maintained good condition for 4 weeks, when they were euthanized. No differences in body weight and food intake were observed between the transposition and control groups. Macroscopic appearance of the stomach and small intestine was normal in both the transposition and control groups, but the cecum was dilated and the new proximal portion of the colon was slightly dilated in the transposition group. This new experimental model will be helpful in examining the mechanism by which different features of the proximal and distal portions of the colon are derived. It will also assist in the research of carcinogenesis in the colon, in determining why the distal portion of the colon is more susceptible to carcinogens, compared with the proximal portion of the colon.