Bradykinin contributes to the vasodilator effects of chronic angiotensin-converting enzyme inhibition in patients with heart failure

Background-Bradykinin, an endogenous vasodilator peptide, is metabolized by ACE. The aims of the present study were to determine the doses of B9340, a bradykinin receptor antagonist, that inhibit vasodilatation to exogenous b radykinin and to assess the contribution of bradykinin to the maintenance o f basal vascular tone in patients with heart failure receiving chronic ACE inhibitor therapy. Methods and Results-Forearm blood flow was measured using bilateral venous occlusion plethysmography. On three occasions in a double-blind randomized manner, 8 healthy volunteers received intrabrachial infusions of placebo or B9340 (at 4.5 and 13.5 nmol/min). On each occasion, placebo or B9340 was c oinfused with bradykinin (30 to 3000 pmol/min) and substance P (4 to 16 pmo l/min). B9340 caused no change in basal FBF but produced dose-dependent inh ibition of the vasodilatation to bradykinin (P <0.001) but not substance P. The effects of bradykinin antagonism were studied in 17 patients with NYHA grade II through IV heart failure maintained on chronic ACE inhibitor ther apy. Incremental doses of B9340, but not HOE-140, produced a dose-dependent vasoconstriction (P=0.01). After withdrawal of ACE inhibitor therapy, B934 0 produced no significant change in forearm blood flow. After reinstitution of therapy, B9340 again resulted in vasoconstriction (P <0.03). Conclusions-B9340 is a potent and selective inhibitor of bradykinin-induced vasodilatation. Bradykinin does not contribute to the maintenance of basal peripheral arteriolar tone in healthy humans or patients with heart failur e but contributes to the vasodilatation associated with chronic ACE inhibit or therapy in patients with heart failure via the B-1 receptor.