Effect of hydrogen peroxide on guinea‐pig tracheal smooth muscle in vitro: role of cyclo‐oxygenase and airway epithelium

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Abstract
1 Hydrogen peroxide (H2O2) (0.1 μm-3 mM) induced variable contractions of guinea-pig isolated trachea which were attenuated by catalase (100 u ml−1) and mannitol (15 mM) suggesting that contractions were induced by H2O2 and/or the hydroxyl anion. 2 Epithelial removal potentiated contractile responses of tracheal preparations to H2O2 with a leftward shift of the concentration-response curve and an increase in the maximal response. 3 Indomethacin (3 μm) inhibited contractions to H2O2 of intact preparations and preparations without epithelium suggesting that contractions may be mediated by cyclo-oxygenase products. Intact preparations (but not preparations without epithelium) contracted in response to high concentrations (>0.1 mM) of H2O2 in the presence of indomethacin suggesting that other excitatory factor(s) released by the epithelium may induce contraction. 4 Preincubation of intact tracheal preparations with H2O2 (1 mM) for 1 h had no effect on responses to histamine or isoprenaline. 5 These results suggest that hydrogen peroxide generated during the inflammatory process may play a role in bronchoconstriction.