Dietary induction of angiotensin-converting enzyme in proximal and distal rat small intestine

Induction of angiotensin-converting enzyme was examined in proximal and dis tal intestinal segments of rats fed a low-protein (4%) diet and then switch ed to a high-protein (gelatin) diet. Animals were killed at varying time po ints, and brush-border membranes and total RNA were prepared from the segme nts. In the proximal intestine, there was a fivefold increase in angiotensi n-converting enzyme levels after 14 days but only a twofold change in mRNA. In the distal intestine, there was no increase in enzyme activity but mRNA increased 2.4-fold. Organ culture was used to measure changes in enzyme bi osynthesis. There was a 5- to 6-fold increase in the biosynthesis of angiot ensin-converting enzyme in the proximal intestine 24 h after the switch to the gelatin diet and a 1.6-fold increase in mRNA levels. No change in biosy nthesis was observed in the distal small intestine despite an increase in m RNA. These results support the conclusion that rapid dietary induction of i ntestinal angiotensin-converting enzyme is differentially regulated in prox imal and distal segments of the small intestine.