The Effect Of Ethanol On Tracheal Smooth Muscle Of Cat

Abstract

Previously we have shown that ethanol induces contraction of pulmonary artery smooth muscle (PASM). However, the effect of ethanol on tracheal smooth muscle (TSM) and the mechanisms involved are not well understood. Therefore, we hypothesized that ethanol induces contractile responses of TSM and extra cellular Ca2+ is involved to this effect. In vitro force measurements were performed in TSM strips, excised from cats (n=29). Tissues were stabilized in Krebs‐Henseleit (KH) solution and treated with different concentrations of ethanol (46 – 276 mM). The role of extra cellular Ca2+ was studied by incubation of tissue in a Ca2+ free KH solution or using a Ca2+ channel blocker‐nifedipine. The role of nitric oxide (NO) was assessed by inhibition of NO synthase (NOS) using Nω‐nitro‐L‐arginine methyl ester. The ethanol induced concentration‐dependent contraction of TSM. Lack of Ca2+ in medium resulted with decrease of TSM tone likewise Ca2+ channel blocker. Inhibition of NOS, significantly increased contractile responses of TSM to the ethanol at lower ad middle concentrations, but reduced these responses at higher concentrations. In addition, inhibition of NOS significantly potentiated TSM tone to ACh.These data demonstrate that ethanol induces TSM contraction of cat and extra cellular Ca2+ is an important involved factor. NO release as a relaxant molecule counteracts the effect of ethanol and other agonists.