Contractile properties of synthetic cationic polypeptides in guinea‐pig isolated trachea

Abstract

The synthetic polypeptides, poly‐l‐arginine, poly‐l‐lysine and poly‐d‐lysine contract guinea‐pig isolated trachea in a concentration‐dependent, epithelium‐independent manner. Indomethacin augmented the contractile response to poly‐l‐arginine. The contractile response to poly‐l‐arginine was not significantly inhibited by nicardipine, a selective l‐type calcium channel blocker or by the histamine H1‐receptor antagonist, mepyramine nor significantly augmented by the neutral endopeptidase inhibitor, phosphoramidon. The contractile response to poly‐l‐arginine was inhibited in a concentration‐dependent manner by prior incubation of guinea‐pig tracheal rings with a number of anionic polypeptides including, low molecular weight heparin, poly‐l‐aspartic acid and bovine serum albumin. In vitro capsaicin‐induced desensitization failed to attenuate the contractile response to poly‐l‐arginine, suggesting little, if any role for sensory neuropeptides in the functional response in the guinea‐pig. Synthetic polypeptides induce an epithelium‐independent, charge‐dependent contraction of guinea‐pig isolated trachea. 1994 British Pharmacological Society