Endopeptidase 24.15 modulates bradykinin-induced contraction in guinea-pig trachea

Guinea-pig tracheal strips were contracted with cumulative concentrations of bradykinin or substance P in the presence of thiorphan, an inhibitor of endopeptidase 24.11 and of angiotensin-converting enzyme, or in the presence of N-[1-(R,S)-carboxy-3-phenylpropyl]Ala-Ala-Phe-para-aminobenzoate (cFP-AAF-pAB), a selective inhibitor of endopeptidase 24.15. The concentration-effect curve of bradykinin was shifted to the left in the presence of each inhibitor whereas the curve of substance P was sensitive to thiorphan but not to cFP-AAF-pAB. These results show that endopeptidase 24.15 may modulate the contractile effect of bradykinin but not that of substance P in the guinea-pig trachea.