bronchorelaxant effect of helicidine, a Helix pomatia extract, involves prostaglandin E2 release

Helicidine is a biological extract prepared from the snail Helix pomatia L. and used in man as an anti-tussive agent. However, its mechanisms of action are not fully defined. In this study, we have investigated a possible relaxant effect of helicidine on guinea-pig airway smooth muscle and evaluated the role of prostanoids and airway epithelium in this relaxation. H. pomatia extract (0.001-1 mg/ml) induced a dose-dependent relaxation of guinea-pig trachea pre-contracted with histamine both in the presence and absence of tracheal epithelium. No significant difference in dose-dependency or magnitude of the relaxation was observed between tracheal segments with or without epithelium (maximal relaxant response of 35 ± 7 and 25 ± 7.5%, respectively). Relaxation of the trachea induced by H. pomatia extract (0.001-1 mg/ml) was inhibited by pretreatment with the cyclooxygenase inhibitor, indomethacin, both in the presence or absence of tracheal epithelium. H. pomatia extract (1 mg/ml) induced a marked and significant increase in prostaglandin E 2 release in tracheal segments with and without epithelium. These results indicate that helicidine possesses a bronchorelaxant activity which is independent of epithelium integrity and which is partly mediated by the release of the relaxant prostanoid, prostaglandin E 2. The origin of prostaglandin E 2 production in the airways remains to be defined.