Effect of aging on the adaptive and proliferative capacity of the small bowel.

Our society is aging at a rapid rate; the effects of aging on physiologic functions (e.g., small bowel adaptation) are poorly understood. The purpose of this study was to determine the ability of the aged small bowel mucosa to adapt after resection. Young (2-month-old) and aged (24-month-old) F344 rats underwent massive (70%) proximal small bowel resection (SBR) or sham operation; rats were killed at 9 or 16 days after surgery. The remnant small bowel and corresponding sham segments were harvested, weighed, and analyzed for DNA content and villus height. To determine whether the adaptive response after SBR could be enhanced, aged rats underwent SBR or sham operation and were treated with either neurotensin or saline solution (control). SBR resulted in adaptive hyperplasia in the remaining small bowel remnant in both young and aged rats at 9 and 16 days compared with sham animals. At 9 days, significant increases were noted in weight, villus height, and DNA content of the distal remnant in young and aged rats after SBR; the increases were similar in both young and aged rats. At 16 days, both young and aged rats displayed significant increases in remnant weight after SBR. Administration of neurotensin increased the weight of the remnant intestine in aged rats after SBR compared with saline treatment. Our findings demonstrate that aged small bowel mucosa exhibits a proliferative and adaptive capacity in response to SBR that was similar to that of the young animals. In addition, neurotensin administration enhanced the normal adaptive response of the small bowel in aged rats, providing further evidence that neurotensin may be therapeutically useful to augment mucosal regeneration in the early periods after massive SBR.