Stimulation of bradykinin B-1 receptors induces vasodilation in conductance and resistance coronary vessels in conscious dogs - Comparison with B-2 receptor stimulation

Background-Constitutive bradykinin B-1 receptors have been identified in do gs; however, their physiological implications involving the coronary circul ation remain to be determined. This study examined, in conscious dogs, the coronary response to des-Arg(9)-bradykinin (a B-1 receptor agonist) and the mechanisms involved. Methods and Results-Eleven dogs were instrumented with a left ventricular m icromanometer, a circumflex coronary catheter, a cuff occluder, a Doppler f low probe, and ultrasonic crystals to measure coronary blood now velocity ( CBFv) and coronary diameter (CD). Intracoronary des-Arg(9)-bradykinin (3 to 100 ng/kg) and bradykinin (0.1 to 10 ng/kg) did not modify systemic hemody namics but dose-dependently increased CBFv and CD, Des-Arg(9)-bradykinin wa s less potent than bradykinin. Hoe 140 (a B-2 antagonist, 10 mu g/kg) aboli shed the effects of bradykinin but did not influence the effects of des-Arg (9)-bradykinin. When CBFv increase was prevented by the cuff occluder, CD r esponses to bradykinin and des-Arg(9)-bradykinin were maintained. Intracoro nary lisinopril (0.75 mg) increased the CD response to bradykinin, with onl y minimal effect on CBFv, and extended the duration of the effect. Lisinopr il did not alter des-Arg(9)-bradykinin responses. Intracoronary N-omega-nit ro-L-arginine (2 mg/kg) decreased the CD effect of bradykinin and prevented the CBFv and CD effects of des-Arg(9)-bradykinin. The relaxing effect of d es-Arg(9)-bradykinin on isolated coronary rings was prevented by des-Arg(9) ,[Leu(8)] -bradykinin. Conclusions-In the conscious dog, B-1 receptors are present in coronary ves sels, and their stimulation produces vasodilation in conductance and resist ance vessels, which is mediated essentially by NO but not modulated by angi otensin-converting enzyme. However, the coronary vasodilation induced by B- 1 receptor stimulation is not as great as that produced by B-2 receptor sti mulation.