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(Hypertension. 2000;35:1226.)
© 2000 American Heart Association, Inc.

Scientific Contributions

In Vitro and In Vivo Inhibition of the 2 Active Sites of ACE by Omapatrilat, a Vasopeptidase Inhibitor

Michel Azizi; Christine Massien; Annie Michaud; Pierre Corvol

From Centre d’Investigations Cliniques 9201, Assistance Publique des Hôpitaux de Paris/INSERM, Hôpital Broussais, Paris, France (M.A., C.M.); and Institut National de la Santé et de la Recherche Médicale, Unité 36, Collège de France, Paris (A.M., P.C.).

Correspondence to Pr Pierre Corvol, INSERM U36, Collège de France, 3 rue d’Ulm, 75005 Paris, France. E-mail corvol{at}infobiogen.fr

Abstract—The vasopeptidase inhibitor omapatrilat inhibits both neutral endopeptidase and angiotensin-converting enzyme (ACE). The in vitro and in vivo inhibitory potency of omapatrilat and the specific ACE inhibitor fosinopril toward the 2 active sites of ACE (called N- and C-domains) was investigated with the use of 3 substrates: angiotensin I, which is equally cleaved by the 2 ACE domains; hippuryl-histidyl-leucine, specific synthetic substrate of the C-domain in high- salt conditions; and a newly synthesized specific substrate of the N-domain designed by acetylating the lysine residue of AcSDKP. In vitro, omapatrilat was 5 times more potent than fosinoprilat in inhibiting angiotensin I hydrolysis. Omapatrilat inhibited similarly both N- and C-domain hydrolysis, whereas fosinoprilat was slightly more specific for the N-domain. The in vivo selective inhibitory potency of single oral doses of 10 mg omapatrilat and 20 mg fosinopril were investigated in a double-blind, placebo-controlled, cross-over study in 9 mildly sodium-depleted normotensive subjects. In accordance with the in vitro results, fosinopril appeared to be more specific for the N-domain than the C-domain in vivo, since plasma and urine AcSDKP concentrations were significantly higher than those observed with omapatrilat. This study shows that it is possible to assess separately in vitro and in vivo the selectivity of ACE or ACE/neutral endopeptidase inhibitors. A differential selectivity may explain some peculiar properties observed with some ACE inhibitors.

Key Words: angiotensin-converting enzyme • angiotensin-converting enzyme inhibitors • AcSDKP • human

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