ACE inhibitors block B(2) receptor desensitization, thereby potentiating
bradykinin beyond blocking its hydrolysis. Angiotensin (Ang)-(1-7) also
acts as an ACE inhibitor and, in addition, may stimulate bradykinin
release via angiotensin II type 2 receptors. In this study we compared the
bradykinin-potentiating effects of Ang-(1-7), quinaprilat, and captopril.
Porcine coronary arteries, obtained from 32 pigs, were mounted in organ
baths, preconstricted with prostaglandin F(2alpha), and exposed to
quinaprilat, captopril, Ang-(1-7), and/or bradykinin. Bradykinin induced
complete relaxation (pEC(50)=8.11+/-0.07, mean+/-SEM), whereas
quinaprilat, captopril, and Ang-(1-7) alone were without effect.
Quinaprilat shifted the bradykinin curve to the left in a biphasic manner:
a 5-fold shift at concentrations that specifically block the C-domain (0.1
to 1 nmol/L) and a 10-fold shift at concentrations that block both
domains. Captopril and Ang-(1-7) monophasically shifted the bradykinin
curve to the left, by a factor of 10 and 5, respectively. A 5-fold shift
was also observed when Ang-(1-7) was combined with 0.1 nmol/L quinaprilat.
Repeated exposure of porcine coronary arteries to 0.1 micromol/L
bradykinin induced B(2) receptor desensitization. The addition of 10
micromol/L quinaprilat or Ang-(1-7) to the bath, at a time when bradykinin
alone was no longer able to induce relaxation, fully restored the relaxant
effects of bradykinin. Angiotensin II type 1 or 2 receptor blockade did
not affect any of the observed effects of Ang-(1-7). In conclusion,
Ang-(1-7), like quinaprilat and captopril, po
