Angiotensin 1-9 and 1-7 potentiated bradykinin-induced nitric oxide liberation from endothelial cells by 2.4-fold and 2.1-fold, respectively, at 10 nmol/L concentrations.
Ang 1-9 and Ang 1-7 potentiate bradykinin action on the B2 receptor, increasing arachidonic acid and NO release, likely via conformational changes in the ACE/B2 receptor complex.
Human heart tissue enzymes cleave angiotensin (Ang) I to release Ang 1-9, Ang II, or Ang 1-7. In atrial homogenate preparations, cathepsin A (deamidase) is responsible for 65% of the liberated Ang 1-9. Ang 1-7 was released (88% to 100%) by a metallopeptidase, as established with peptidase inhibitors. Ang II was liberated to about equal degrees by ACE and chymase-type enzymes. Cathepsin A's presence in heart tissue was also proven because it deamidated enkephalinamide substrate by immunoprecipitation of cathepsin A with antiserum to human recombinant enzyme and by immunohistochemistry. In immunohistochemistry, cathepsin A was detected in myocytes of atrial tissue. The products of Ang I cleavage, Ang 1-9 and Ang 1-7, potentiated the effect of an ACE-resistant bradykinin analog and enhanced kinin effect on the B(2) receptor in Chinese hamster ovary cells transfected to express human ACE and B(2) (CHO/AB), and in human pulmonary arterial endothelial cells. Ang 1-9 and 1-7 augmented arachidonic acid and nitric oxide (NO) release by kinin. Direct assay of NO liberation by bradykinin from endothelial cells was potentiated at 10 nmol/L concentration, 2.4-fold (Ang 1-9) and 2.1-fold (Ang 1-7); in higher concentrations, Ang 1-9 was significantly more active than Ang 1-7. Both peptides had traces of activity in the absence of bradykinin. Ang 1-9 and Ang 1-7 potentiated bradykinin action on the B(2) receptor by raising arachidonic acid and NO release at much lower concentrations than their 50% inhibition concentrations (IC(50)s) with ACE. They probably induce conformational changes in the ACE/B(2) receptor complex via interaction with ACE.
Jackman et al. (Wed,) reported a other. Angiotensin 1-9 and 1-7 was evaluated on Nitric oxide (NO) liberation by bradykinin. Angiotensin 1-9 and 1-7 potentiated bradykinin-induced nitric oxide liberation from endothelial cells by 2.4-fold and 2.1-fold, respectively, at 10 nmol/L concentrations.