Hydrolysis of Angiotensin Peptides by Human Angiotensin I–Converting Enzyme and the Resensitization of B 2 Kinin Receptors

Abstract

We measured the cleavage of angiotensin I (Ang I) metabolites by angiotensin I–converting enzyme (ACE) in cultured cells and examined how they augment actions of bradykinin B2 receptor agonists. Monolayers of Chinese hamster ovary cells transfected to stably express human ACE and bradykinin B2 receptors coupled to green fluorescent protein (B2GFP) or to express only coupled B2GFP receptors. We used 2 ACE-resistant bradykinin analogues to activate the B2 receptors. We used high-performance liquid chromatography to analyze the peptides cleaved by ACE on cell monolayers and found that Ang 1-9 was hydrolyzed 18× slower than Ang I and &30% slower than Ang 1-7. Ang 1-7 was cleaved to Ang 1-5. Although μmol/L concentrations of slowly cleaved substrates Ang 1-7 and Ang 1-9 inhibit ACE, they resensitize the desensitized B2GFP receptors in nmol/L concentration, independent of ACE inhibition. This is reflected by release of arachidonic acid through a mechanism involving cross-talk between ACE and B2 receptors. When ...