title: In vivo measurement of coronary circulation angiotensin-converting enzyme activity in humans.
abstract: Angiotensin-converting enzyme (ACE) is present on the luminal surface of the coronary vessels, mostly on capillary endothelium. ACE is also expressed on coronary smooth muscle cells and on plaque lipid-laden macrophages. Excessive coronary circulation (CC)-ACE activity might be linked to plaque progression. Here we used the biologically inactive ACE substrate (3)H-labeled benzoyl-Phe-Ala-Pro ([(3)H]BPAP) to quantify CC-ACE activity in 10 patients by means of the indicator-dilution technique. The results were compared with atherosclerotic burden determined by coronary angiography. There was a wide range of CC-ACE activity as revealed by percent [(3)H]BPAP hydrolysis (30-74%). The atherosclerotic extent scores ranged from 0.0 to 66.97, and the plaque area scores ranged from 0 to 80 mm(2). CC-ACE activity per unit extracellular space (V(max)/K(m)V(i)), an index of metabolically active vascular surface area, was correlated with myocardial blood flow (r = 0.738; P = 0.03) but not with measures of the atherosclerotic burden. These results show that CC-ACE activity can be safely measured in humans and that it is a good marker of the vascular area of the perfused myocardium. It does not, however, reflect epicardial atherosclerotic burden, suggesting that local tissue ACE may be more important in plaque development.
authors.affiliation: Montreal Heart Institute and University of Montreal, Quebec, Canada H3G 1A4.
authors.forename: Cezar
authors.initials: C
authors.lastname: Staniloae
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Schwab
authors.forename: Andre
authors.initials: A
authors.lastname: Simard
authors.forename: Richard
authors.initials: R
authors.lastname: Gallo
authors.forename: Ihor
authors.initials: I
authors.lastname: Dyrda
authors.forename: Gilbert
authors.initials: G
authors.lastname: Gosselin
authors.forename: Jacques
authors.initials: J
authors.lastname: Lesperance
authors.forename: James W
authors.initials: JW
authors.lastname: Ryan
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Dupuis
mesh_terms: D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000175:diagnosis / Q000000981:diagnostic imaging; D003326:Coronary Circulation; D006801:Humans; D006868:Hydrolysis; D008955:Models, Cardiovascular; D009842:Oligopeptides / Q000378:metabolism; D007703:Peptidyl-Dipeptidase A / Q000097:blood*
chemical_list: D009842:Oligopeptides; C029689:benzoylphenylalanyl-alanyl-proline; D007703:Peptidyl-Dipeptidase A