Evidence for tissue angiotensin-converting enzyme in explanted hearts of ischemic cardiomyopathy using targeted radiotracer technique

This study aimed to determine the magnitude and distribution of tissue angiotensin-converting enzyme (ACE), mast-cell chymase, and angiotensin II, type 1, plasmamembrane 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-mm contiguous short-axis slices of explanted hearts from 3 patients with ischemic cardiomyopathy were incubated in vitro with FBL, with and without 1026 M lisinopril. Tissue radioac-tivity 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