d‐Arg[Hyp3‐Thi5‐d‐Tic7‐Tic8]‐bradykinin, a potent antagonist of smooth muscle BK2 receptors and BK3 receptors

d‐Arg[Hyp3‐Thi5‐d‐Tic7‐Tic8]‐bradykinin (NPC 16731) inhibited bradykinin (BK) binding and BK‐induced contraction in guinea‐pig ileum, being markedly more potent than d‐Phe7‐BK analogues as a BK2 receptor antagonist. In isolated trachea NPC 16731, unlike other BK2 antagonists, inhibited BK binding and BK‐induced contraction, and 45Ca2+ efflux in tracheal smooth muscle cells. That NPC 16731 potently inhibits BK effects in trachea provides further evidence for the existence of the airway BK3 receptor.