Bradykinin metabolism in the postinfarcted rat heart: role of ACE and neutral endopeptidase 24.11

The respective role of angiotensin-converting enzyme (ACE) and neutral endo peptidase 24.11 (NEP) in the degradation of bradykinin (BK) has been studie d in the infarcted and hypertrophied rat heart. Myocardial infarction (MI) was induced in rats by left descendant coronary artery ligature. Animals we re killed, and hearts were sampled 1, 4, and 35 days post-MI. BK metabolism was assessed by incubating synthetic BK with heart membranes from sham hea rts and infarcted (scar) and noninfarcted regions of infarcted hearts. The half-life (t 1/2) of BK showed significant differences among the three type s of tissue at 4 days [sham heart (114 +/- 7 s) > noninfarcted region (85 /- 4 s) > infarcted region (28 +/- 2 s)] and 35 days post-MI [sham heart (1 43 +/- 6 s) = noninfarcted region (137 +/- 9 s) > infarcted region (55 +/- 4 s)]. No difference was observed at 1 day post-MI. The participation of AC E and NEP in the metabolism of BK was defined by preincubation of the membr ane preparations with enalaprilat, an ACE inhibitor, and omapatrilat, a vas opeptidase inhibitor that acts by combined inhibition of NEP and ACE. Enala prilat significantly prevented the rapid degradation of BK in every tissue type and at every sampling time. Moreover, omapatrilat significantly increa sed the t 1/2 of BK compared with enalaprilat in every tissue type and at e very sampling time. These results demonstrate that experimental MI followed by left ventricular dysfunction significantly modifies the metabolism of e xogenous BK by heart membranes. ACE and NEP participate in the degradation of BK since both enalaprilat and omapatrilat have potentiating effects on t he t 1/2 of BK.