The mechanisms of ethanol‐induced contraction of tracheal smooth muscle

We have shown that ethanol induces contraction of pulmonary artery smooth muscle. Therefore, we hypothesized that ethanol induces contractile responses of tracheal smooth muscle and extra cellular Ca 2+ plays an important role on these responses. In vitro force measurements were performed in tracheal smooth muscle strips obtained from adult ferrets (n=33). TSM strips were treated with different concentration of ethanol (46 ‐ 322 mM). In another set of experiments strips were incubated in Ca 2+ free Krebs ‐Hensleit solution or a Ca 2+ channel blocker ‐ nifedipine was used and then treated with ethanol. The involvement of nitric oxide (NO) was studied by inhibition of nitric oxide synthase (NOS) using N ω ‐nitro‐L‐arginine methyl ester. The ethanol induced concentration‐dependent contraction of TSM. Prior treatment of tissues with a single dose of ethanol increased the contractile responses of TSM to acetylcholine (p<0.05). Lack of Ca 2+ in medium resulted with decrease of contractile force of the TSM likewise Ca 2+ channel blocker. Inhibition of NOS significantly increased contractile responses (p<0.001). These data demonstrate that ethanol induces contraction of TSM and it appears to play a critical role in enhancing cholinergically mediated contractile responses of TSM. Extra cellular Ca 2+ plays an important role on these responses and NO release as a relaxant molecule counteracts the effects of ethanol on TSM.