Inhibition of bradykinin-induced bronchoconstriction in the guinea-pig by a synthetic B2 receptor antagonist.

1. Intravenous bradykinin (Bk) elicited bronchoconstriction in the anaesthetized ventilated guinea-pig which was not mimicked by the B1 receptor agonist, des-Arg9-Bk. 2. Bradykinin-induced bronchoconstriction was inhibited by the B2 receptor antagonist B4881, but not by the B1 receptor antagonist des-Arg9-Leu8-Bk. The effect of B4881 was short-lived. 3. The B2 receptor antagonist as B4881 was selective for bradykinin as B4881 did not significantly inhibit bronchoconstriction induced by i.v. bombesin, platelet activating factor, acetylcholine, histamine or vagal stimulation. 4. These results suggest that bradykinin-induced bronchoconstriction in the guinea-pig is via activation of a B2 receptor population and that B4881 is a selective B2 antagonist that may be useful for investigating the involvement of bradykinin in the lung.