Endothelin-induced constriction of guinea pig airways: role of platelet-activating factor

Endothelin-1 (ET-1, 1-100 nM) evoked a concentration-dependent contraction of guinea pig trachea and upper bronchi in vitro. The response was significantly attenuated by BN 52021 (ginkgolide B, 10 microM), a specific receptor antagonist to platelet-activating factor. Precontraction of the tissues with endothelin (50 nM) desensitized tissues to platelet-activating factor (200 nM), while preincubation of the tissues with platelet-activating factor slightly inhibited the response to endothelin. These findings suggest that platelet-activating factor may mediate endothelin-induced airway contraction in the guinea pig.