Efeitos da acariçoba (Hydrocotyle umbellata L.) sobre as vias aéreas isoladas de ratos

Abstract

Although the acariçoba Hydrocotyle umbellate L. – Araliaceae has important biological effects, including reports in the literature for the treatment of asthma, its actions on the respiratory system have not been verified. The goals of this work were to determine the effects of the hydro-alcoholic extract of the underground H. umbellata (HEHU) on tracheal smooth muscle isolated from rats. For this, tracheal rings were prepared separately in an organ bath to record the isometric tension. The relaxing effects of HEHU on tracheas, the influence of NO/GCs and COX/prostanoid pathways, K+ channels, extracellular Ca2+ influx and synergism between HEHU and nitric oxide donor drug and β-adrenergic agonist were also evaluated. The results show that HEHU induces airway smooth muscle relaxation in a dose-dependent manner (0-700 µg/mL). The pre-treatment with NO synthase and guanylyl ciclase inhibitors (L-NAME and ODQ, respectively), K+ channel blockes (tetraethylammonium) and COX inhibitor (sodium diclofenac) did not alter the relaxation induced by HEHU. Carbachol-stimulated contraction was impaired by previous treatment with HEHU. The HEHU also inhibited the contraction caused by the influx of Ca2+ stimulated by carbachol and KCl (75 mM). No synergism was observed between nitric oxide-stimulated relaxation or activation of β-adrenergic receptors and HEHU. In conclusion, HEHU induces airways smooth muscle dilatation isolated from rats and the blocking of Ca2+ influx through the cell membrane seems to be the main mechanism of action responsible for this effect.