EFFECTS OF BRADYKININ RECEPTOR AGONISTS, AND CAPTOPRIL AND THIORPHAN IN FERRET ISOLATED TRACHEA - EVIDENCE FOR BRADYKININ GENERATION IN-VITRO

Bradykinin B-2 receptor agonists, but not a B-1 receptor agonist, were potent spasmogens of ferret isolated trachea. Bradykinin-induced cont ractions were unaffected by several pharmacological agents, indicating a direct effect on airway smooth muscle B-2 receptors. Captopril plus thiorphan caused contractions in approximately 70% of preparations th at were abolished by B-2 receptor antagonists, but not by B-1 receptor antagonist. Thus, ferret tracheal tissues appear capable of releasing and degrading kinins in vitro. Inhibition of peptide degradation with captopril and thiorphan may allow the endogenous kinins to accumulate in concentrations sufficient to elicit tracheal contraction via activ ation of B-2 receptors.