Actions of some peptides on bronchial muscle.

The decapeptide kallidin-10, substance P and angiotensin increased the resistance of guinea-pig lungs to inflation; lysine- or arginine-vasopressin and oxytocin were inactive. Acetylsalicylate antagonized this action of kallidin-10, as it does that of bradykinin, but it failed to antagonize substance P or angiotensin. Bradykinin also increased resistance to inflation of rabbit lungs and, to a lesser extent, rat lungs. It caused a relatively slow contraction of guinea-pig tracheal and bronchial muscle in vitro, but it did not contract isolated rabbit, dog or human bronchus. The relative potencies of different substances on different bronchial test preparations, and also in different species, were not parallel.