Objectives: Angiotensin converting enzyme (ACE) has been shown to be an important peptidasse that play a role in digestion and assimilation of protein rich in proline such as casein, gliadin and collagen. Despite that ACE inhibitors have been popular for various types of hypertension and congestive heart failure, the effects of their long-term treatment on intestinal ACE activities are not known. Therefore, we measured intestinal specific activities in rats after four weeks' treatment of ACE inhibitors.
Methods: Thirty Wistar rats weighing about 200g in average were divided into three groups, and supplied with tap water, captopril solution and enalapril solution respectively for four weeks. After sacrificing, intestinal ACE specific activities were measured in homogenate and brush border membrane fraction respectively, which was prepared from three equally divided segments of removed small intestine.
Results: ACE specific activities of proximal, middle and distal segments of control group were 178.6 +/- 64.2, 180.3 +/- 60.2 and 48.6 +/- 13.1 in brush border membrane (mean +/- SD, nmol/min/mg protein) respectively. Those of captopril group were 314.2 +/- 72.5, 281.0 +/- 69.8 and 67.7 +/- 21.8 respectively, showing tendency of increase in proximal and middle segments (p < 0.01 and 0.05 respectively). By contrast, those of enalapril group were 48.5 +/- 27.6, 70.7 +/- 15.6 and 11.6 +/- 4.4 respectively, which were significantly lower (p < 0.01) than those of control group.
Conclusion: Rat intestinal ACE specific activities were not inhibited by captopril treatment, but inhibited by enalapril treatment. This finding may explain why there has not been any case report of malabsorption in patients taking captopril. But the malabsorption of prolyl peptide could be possible in cases with long-term administration of enalapril.