Morphological effects of transposing a segment of transverse colon into the ileum of the Holtzman rat.

In order to determine if the rat colon is capable of adaptation when placed in another location within the intestinal tract and/or subject to different luminal contents, a 3 cm segment of transverse colon was transposed into the ileum. Sixteen days later, the animals were injected with tritiated thymidine (1 microCi/g body weight) and killed one hour later. Autoradiographs were analyzed for number of cells per crypt column, number of labeled cells per crypt column, position of labeled cells in the crypt column, and formation of Paneth cells or villi in the transposed colon. Proliferative activity of the epithelium was measured by isolating whole crypts and determining disintegrations per minute per crypt. Except for alterations in the positions of labeled cells, as determined by crypt profiles, no changes from normal were observed in any of the parameters measured. Hence, unlike the small bowel, the colon is refractory to the influences of a new environment.