DIETARY-REGULATION OF RAT INTESTINAL ANGIOTENSIN-CONVERTING ENZYME AND DIPEPTIDYL PEPTIDASE-IV

The small intestinal brush-border membrane contains several peptidases that are involved in the hydrolysis of dietary peptides containing pr oline. A high-proline (gelatin) diet was administered to one of severa l groups of rats to study its possible regulatory effect on levels of two prolyl peptidases, namely angiotensin-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP IV). Groups of rats were maintained on is ocaloric diets containing either low (4%), normal (17%), or high (50%) protein (casein) or high (50%) gelatin. After 7 days, brush-border me mbranes and total RNA were prepared from the small intestine. ACE acti vity was 3- to 10-fold higher in brush-border membranes from the gelat in group compared with the low-protein group. DPP IV exhibited a three - to sixfold increase. Immunoblot analysis of brush-border membrane-as sociated ACE protein indicated a six- to eightfold increase in the hig h-gelatin group. There was also a 1.5- to 3-fold increase in steady-st ate levels of ACE and DPP IV mRNA. These results suggest that a diet h igh in proline (gelatin) is particularly effective in increasing intes tinal levels of these two enzymes.