Modification of the Intestinal Postirradiation Proliferative Response by Intraabdominal H-4-II-E2 Tumors

Intraperitoneal injection of H-4-II-E/sub 2/ tumor cells gave rise to a number of individually growing intraabdominal tumors concentrated at sites of high abdominal vascularization. During tumor growth, both tumor and intestinal crypt cell proliferative activity were progressively depressed. A linear reduction of (/sup 3/H)TdR incorporation occurred in individual tumors independent of tumor size, suggesting that total tumor burden determines the proliferative status of individual tumors. Cytokinetic jejunal crypt analyses indicated that both a reduction in crypt cellularity and an abbreviated cell cycle transit time were noted during the depression of proliferative activity in the jejunum. In tumor-bearing rats the migration rate of cells from the jejunal crypt through the villus was reduced in response to a reduction in total cell production in the crypt. The life span of the epithelial cell in both tumor-bearing and normal rats was similar due to a reduction in villus cellularity in the tumor-bearing animals. Following abdominal irradiation of the tumor, the magnitude, but not the time course of hyperproliferative intestinal recovery, was influenced by the tumor mass. For nontumor-bearing animals, maximal hyperproliferation (>200% of control) occurred 96 hr postradiation. With increasing tumor burden the compensatory proliferative response to radiation was progressively reduced.