Ileal crypt cell population kinetics after 40% small bowel resection. Autoradiographic studies in the rat.

Ileal crypt cell population kinetics were investigated by autoradiography with tritiated thymidine in rats 60 days after resection of a jejunal segment equivalent to 40% of the length of the small bowel. Controls were subjected to transection and anastomosis. The mean total number of cells and the mean number of labeled cells per crypt cell column were estimated. The distribution of proliferating cells was obtained by determining the percentage of labeled cells at each cell position in the crypt cell columns. The cell cycle was analyzed by the method of percentage-labeled metaphases. The mean total number of cells was increased from 30.5 to 36.6 (P less than 0.002) and the mean number of labeled cells per crypt cell column was increased from 10.2 to 12.4 (P less than 0.001). Labeling index was unaltered. The mean sizes of the proliferative and maturation zones were increased (P less than 0.002). The estimated median duration of the cell cycle was 11.5 hr in the control group and 10.5 hr in the resection group. The duration of DNA synthesis was 6.4 hr in both groups. It is concluded that 40% small bowel resection increases cell renewal by expanding the size of the proliferative zone of the crypt cell population.