Apoptosis and the pattern of DNase I expression following massive small bowel resection

Introduction. Following massive small bowel resection (SBR), histologic evidence of increased enterocyte apoptosis has been demonstrated in several animal models. Deoxyribonuclease I (DNase I) is requisite for intranuclear cleavage of DNA during apoptosis; we therefore hypothesized that the expression of this gene would be increased following SBR. Methods. Male ICR mice underwent either 50% proximal SBR or sham surgery (bowel transection/reanastomosis). After 12 h and 1, 3, and 7 days, rates of enterocyte proliferation and apoptosis were recorded as well as DNase I mRNA expression and activity. Results. Adaptation after SBR was confirmed at each time point by increased proliferation. Enterocyte proliferation was increased by 12 h and apoptosis was increased by 24 h and remained elevated through Day 7, When compared with sham-operated mice, SBR resulted in a twofold increase in both DNase I expression and activity at 24 h postoperatively, which returned to baseline by Postoperative Day 3. Conclusions. DNase I expression and activity are increased early following massive SBR but return to baseline despite persistent increased rates of enterocyte apoptosis and proliferation. This enzyme may be important in the early induction of apoptosis following massive SBR, but not once anew set point has been established in the balance between the rate of enterocyte production and enterocyte loss. (C) 1999 Academic Press.