In-vitro and in-vivo inhibition of rat neutral endopeptidase and angiotensin converting enzyme with the vasopeptidase inhibitor gemopatrilat

Objectives Vasopeptidase inhibitors are single molecules that simultaneously inhibit neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE). The aim of this study was to characterize in-vitro and in-vivo inhibition of NEP and ACE in the rat with the vasopeptidase inhibitor gemopatrilat. Design and methods In-vitro NEP and ACE inhibition was studied by radioinhibitory binding assay using rat renal membranes and the specific NEP inhibitor radioligand 125 I-RB104 and the specific ACE inhibitor radioligand 125 I-MK351A, respectively (n = 3 per curve). In-vivo NEP and ACE inhibition was studied using in-vitro autoradiography in rats that received oral gemopatrilat (1, 3, 10 mg/kg; n = 4 per dose) and were killed 1 h later, or received oral gemopatrilat (3, 10 mg/kg) and were killed at time points 1, 2, 4, 8, 18, 24 and 48 h (n = 4 per time point). Results Gemopatrilat caused a concentration-dependent displacement of specific radioligands from renal membrane NEP (IC 50 305 ± 5.4 nmol/l) and ACE (IC 50 3.6 ± 0.02 nmol/l). In the dose-response study gemopatrilat (1, 3 and 10 mg/kg) caused significant inhibition of plasma ACE (P < 0.01), and renal ACE and NEP (3,10 mg/kg, P < 0.01). In the time course experiment gemopatrilat (10 mg/kg) increased plasma renin activity for 8 h (P < 0.01) and inhibited plasma ACE (P < 0.05), renal NEP (P < 0.01) and renal ACE (P < 0.05) for 48 h. Conclusions Gemopatrilat is a potent in-vitro vasopeptidase inhibitor that also causes prolonged inhibition of circulating and renal ACE and renal NEP after a single oral dose. The data suggest that gemopatrilat may be a useful addition to existing vasopeptidase inhibitors in the treatment of cardiovascular disease.