Bradykinin and human airways

This work explored the effects of bradykinin (BK) on human airways. Bradykinin (1 mug/kg body weight) was rapidly injected intravenously and respiratory system resistance (Rrs), closing volume (CV), forced vital capacity (FVC), expiratory volume in the first second (FEV1) maximal midexpiratory flow (MMF), and peak flow (PF) were measured. Bradykinin in normals produced no changes in Rrs or CV, but reduced the FVC. This suggests alveolar duct constriction, since no constriction of either large or small airways occurred with the decreased FVC. Bradykinin in asthmatics decreased the Rrs and CV, and increased the FEV1, MMF and PF, while the FVC did not change significantly. The absence of a significant increase in the FVC in the presence of concomitant bronchodilation, suggests that asthmatics also had alveolar duct construction. These data are consistent with animal studies which show that BK may release adrenalin (or other agents) with secondary effects, such as bronchodilation. The secondary bronchodilation seen in asthmatics but not in normals, is probably a result of the initial higher intrinsic bronchial tone of the asthmatics.