CONTRACTILE PROPERTIES OF SYNTHETIC CATIONIC POLYPEPTIDES IN GUINEA-PIG ISOLATED TRACHEA

1 The synthetic polypeptides, poly-L-arginine, poly-L-lysine and poly- D-lysine contract guinea-pig isolated trachea in a concentration-depen dent, epithelium-independent manner. Indomethacin augmented the contra ctile response to poly-L-arginine. 2 The contractile response to poly- L-arginine was not significantly inhibited by nicardipine, a selective L-type calcium channel blocker or by the histamine H-1-receptor antag onist, mepyramine nor significantly augmented by the neutral endopepti dase inhibitor, phosphoramidon. 3 The contractile response to poly-L-a rginine was inhibited in a concentration-dependent manner by prior inc ubation of guinea-pig tracheal rings with a number of anionic polypept ides including, low molecular weight heparin, poly-L-aspartic acid and bovine serum albumin. 4 In vitro capsaicin-induced desensitization fa iled to attenuate the contractile response to poly-L-arginine, suggest ing little, if any role for sensory neuropeptides in the functional re sponse in the guinea-pig. 5 Synthetic polypeptides induce an epitheliu m-independent, charge-dependent contraction of guineapig isolated trac hea.