Onset of cell proliferation in the shortened gut. Rapid hyperplasia after jejunal resection.

Early manifestations of cell proliferation were studied in the large and small bowel of young female rats after resection of the proximal one-third of the small bowel. On the 2nd day after resection, the absolute amounts of RNA and DNA increased in gut distal to the resection. As compared with values from sham-resected gut, nucleic acid levels in much of the distal small bowel and colon increased. Increased specific activity in DNA after injection of [3H]thymidine was present in the small bowel on the 2nd day. Changes were marked and persistent in midgut for 10 days, tending to be less intense and of shorter duration in segments progressively more distal. Compensatory cell proliferation in midgut occurs within 2 days of jejunectomy.