title: Evidence for tissue angiotensin-converting enzyme in explanted hearts of ischemic cardiomyopathy using targeted radiotracer technique.
abstract: This study aimed to determine the magnitude and distribution of tissue angiotensin-converting enzyme (ACE), mast-cell chymase, and angiotensin II, type 1, plasma membrane receptor (AT1R), in relation to collagen replacement in infarcted and noninfarcted left ventricular myocardial segments. A new radiotracer, 18F-fluorobenzoyl-lisinopril (FBL), was synthesized without compromising its affinity for tissue ACE.
  
  
  METHODS
  Five- to 10-microm contiguous short-axis slices of explanted hearts from 3 patients with ischemic cardiomyopathy were incubated in vitro with FBL, with and without 10(-6) M lisinopril. Tissue radioactivity was recorded as a function of position in photostimulating luminescence units (PSL). Immunohistochemistry studies were performed with mouse monoclonal antibody against ACE, anti-mast cell chymase, and polyclonal antibody against the human AT1R.
  
  
  RESULTS
  There was specific binding of FBL to ACE; mean FBL binding was 6.6 +/- 5.2 PSL/mm2, compared with 3.4 +/- 2.5 PSL/mm2 in segments incubated in solution containing cold, 10(-6) M lisinopril (P < 0.0001). Mean FBL binding was 6.3 +/- 4.5 PSL/mm2 in infarcted, 7.6 +/- 4.7 PSL/mm2 in periinfarcted, and 5.0 +/- 1.0 PSL/mm2 in remote, noninfarcted (P < 0.02 vs. periinfarcted) segments. The autoradiographic observations concerning FBL binding were confirmed by ACE and AT1R immunoreactivity. Distribution of mast cell chymase differed from ACE, as a higher number of mast cells was present in the remote, noninfarcted myocardium than in the periinfarcted myocardium (5.1 +/- 3.2 vs. 3.2 +/- 2.2 mast cells per field, P < 0.001). The number of mast cells in ischemic hearts exceeded that in normal hearts (4.2 +/- 2.7 vs. 1.5 +/- 1.2 mast cells per field, x200, P < 0.001).
  
  
  CONCLUSIONS
  FBL binds specifically to ACE. The binding is nonuniform in infarcted, periinfarcted, and remote, noninfarcted segments, and there is apparently increased ACE activity in the juxtaposed areas of replacement fibrosis. On the other hand, the distribution of mast cell chymase appears nonuniform and disparate from ACE.
authors.affiliation: Division of Nuclear Medicine, the University of Maryland Hospital and School of Medicine, Baltimore, Maryland, USA. vdilsizian@umm.edu
authors.forename: Vasken
authors.initials: V
authors.lastname: Dilsizian
authors.forename: William C
authors.initials: WC
authors.lastname: Eckelman
authors.forename: Maria L
authors.initials: ML
authors.lastname: Loredo
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Jagoda
authors.forename: Jamshid
authors.initials: J
authors.lastname: Shirani
mesh_terms: D000804:Angiotensin II / Q000378:metabolism; D001345:Autoradiography; D053818:Chymases / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D017706:Lisinopril / Q000031:analogs & derivatives; D008297:Male; D008407:Mast Cells / Q000201:enzymology; D017202:Myocardial Ischemia / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D019275:Radiopharmaceuticals; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism
chemical_list: C518564:18F-fluorobenzoyl-lisinopril; D019275:Radiopharmaceuticals; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; D003094:Collagen; D017706:Lisinopril; D007703:Peptidyl-Dipeptidase A; D053818:Chymases