Modulation of mouse intestinal epithelial cell turnover in the absence of angiotensin converting enzyme

Angiotensin converting enzyme (ACE) has been shown to be involved in regulation of apoptosis in nonintestinal tissues. This study examined the role of ACE in the modulation of intestinal adaptation utilizing ACE knockout mice ([ACE.sup.-/-]). A 60% small bowel resection (SBR) was used, since this model results in a significant increase in intestinal epithelial cell (EC) apoptosis as well as proliferation. Baseline villus height, crypt depth, and intestinal EC proliferation were higher, and EC apoptosis rates were lower in [ACE.sup.-/-] compared with [ACE.sup.+/+] mice. After SBR, EC apoptosis rates remained significantly lower in [ACE.sup.-/-] compared with [ACE.sup.+/+] mice. Furthermore, villus height and crypt depth after SBR continued to be higher in [ACE.sup.-/-] mice. The finding of a lower bax-to-bcl-2 protein ratio in [ACE.sup.-/-] mice may account for reduced EC apoptotic rates after SBR in [ACE.sup.-/-] compared with [ACE.sup.+/+] mice. The baseline higher rate of EC proliferation in [ACE.sup.-/-] compared with [ACE.sup.+/+] mice may be due to an increase in the expression of several EC growth factor receptors. In conclusion, ACE appears to have an important role in the modulation of intestinal EC apoptosis and proliferation and suggests that the presence of ACE in the intestinal epithelium has a critical role in guiding epithelial cell adaptive response. short bowel syndrome; bax; bcl-2; intestine; adaptation