Compensation by the residual intestine after intestinal resection in the rat. II. Influence of postoperative time interval.

The sequence of events which comprise the early response of the residual intestine to 70% resection of the combined jejunum and ileum was investigated. Animals were killed at 2,4,6,8, and 12 postoperative days. Marked increases in DNA synthesis expressed as disintegraions per minute per crypt, cells per cyrypt column, labeled cells per crypt column, thickness of intestinal wall components, and cells per villus column were apparent as early as 2 to 4 postoperative days. By 12 days, the values had reached the 30-day postoperative levels found in earlier experiments, indicating that a new steady state had already been reached. Jejunal and ileal crypts responded nearly the same during the first 12 days with their sizes increasing to about 150% of control values. However, although jejunal villus cell counts increased to 125% of controls, the ileal villus cell counts increased to 180% of controls, indicating that the sizes of the two crypt and villus epithelial cell populations are independently controlled.