Induction of Intestinal Carcinoma in the Rat by X-Irradiation of the Small Intestine

The exteriorized ileum and jejunum of maie Holtzman rats were x irradiated with doses from 1000 to 2500 r. The superior mesenteric artery and vein were clamped during radiation exposure in about haif of the irradiated animals. Thirty-day survival and appearance of intestinal tumors in the 12 months post-irradiation were noted. Per cent survival at 30 days was increased by the blood restriction procedure in all cases where there was some mortality due to irradiation alone. Over 50% of the irradiated animals that survived exposure doses above 1400 r because of the clamping procedure developed intestinal tumors. Radiation alone induced the neoplasm in only the 1400-r group. Tumors appeared as early as 55 days and as late as 225 days postirradiation. Animals without surgery or irradiation and those subjected to the intestinal vessel clamping procedure alone did not develop tumors. The neoplasm has features of adenocarcinoma including invasion of submucosal and muscle layers of the gut, but the possibility that the apparent invasion of fibrous tissue by epithelium is due to trapping of epithelium still exists in some animals. Glandular epithelium in the diaphragm of one rat with an intestinal tumor and apparent neoplastic glands in the gut mesentery of another was found. There is little, if any, doubt that these represent metastases. It was not possible to transplant the tumor into normal animals. (auth)