Experimental colon cancer in the absence of intestinal contents in Sprague-Dawley rats.

The proximal and distal ends of the transverse colons of 16 noninbred Sprague-Dawley rats were severed and stitched to their abdominal walls. The ascending and descending colons were anastomosed end-to-end. The disarticulated colon loop was rinsed 30 times over 15 days to remove all traces of dimethylhydrazine (21 mg/kg body wt) for 27 weeks. When rats were killed 3 weeks later, 4 had invasive carcinomas and 2 had tubular adenomas in the end-to-end anastomosed (function-isolated) colons. Three rats developed invasive carcinomas in the isolated (defunctionalized) colon loops. The carcinogen probably reached the isolated colon loop through the circulation and induced (independently of bile acids) mucosal changes that led to invasive carcinoma.