The effect of acute angiotensin-converting enzyme and neutral endopeptidase 24.11 inhibition on plasma extravasation in the rat

The effect of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) inhibition on microvascular plasma leakage (extravasation) was evaluated in a rat model. Progressive inhibition of ACE using captopril caused increased extravasation when lung ACE was inhibited by >55%. In contrast, the selective inhibition of renal NEP by >90% using ecadotril did not increase extravasation. In NEP-inhibited rats, extravasation produced by the ACE inhibitors captopril and lisinopril was markedly enhanced. The dual ACE and NEP inhibitor omapatrilat, at oral doses of 0.03, 0.1, and 0.3 mg/kg, selectively inhibited lung ACE by 19, 61, and 76%, respectively, and did not cause significant extravasation. Doses of 1 and 10 mg/kg omapatrilat, which produced >90% inhibition of ACE and also inhibited renal NEP by 54 and 78%, respectively, significantly increased extravasation. In this model, bradykinin and substance P produced extravasation that could be abolished by the bradykinin 2 (132) receptor antagonist Hoe 140 (icatibant) or the neurokinin 1 (NK1) antagonist CP99994 [(+)(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine], respectively. Bradykinin induced extravasation was also partially (similar to40%) inhibited by CP99994, indicating that a portion of the response involves B2 receptor-mediated release of substance P. In conclusion, this study is the first to relate the degree of ACE and/or NEP inhibition to extravasation liability in the rat model. Our data clearly demonstrate that ACE inhibitor-induced plasma extravasation is enhanced by concomitant inhibition of NEP. In addition, this study provides further evidence for the role for B2 and NK1 receptors in mediating plasma extravasation in the rat.