The aims of the study were to investigate the short and long-term effects of Provinol (red wine polyphenolic compounds) on tracheal smooth muscle reactivity using an in-vitro model of ovalbumin-induced airway inflammation in guinea-pig trachea, and to evaluate the role of nitric oxide (NO) in the bronchodilatory effect of Provinol. The amplitude of tracheal smooth muscle contraction in response to mediators of bronchoconstriction - histamine (10 nM-1 mM), acetylcholine (10 nM-1 mM) and to allergen (ovalbumin 10(-5)-10(-3) g mL(-1)) was used as a parameter of tracheal smooth muscle reactivity. To test the short-term effects of Provinol, isolated tracheal strips were pre-treated for 30 min with Provinol (10(-4) mg mL(-1)) alone or in combination with Nomega-nitro-L-arginine methyl ester (L-NAME; 10(-6) mol L(-1)). To test the long-term effects of Provinol, isolated tracheal strips were prepared from guinea pigs that had been treated for 14 days with Provinol (20 mg kg(-1) per day) alone or in combination with L-NAME (40 mg kg(-1) per day). Incubation of tracheal smooth muscle with Provinol decreased the amplitude of contraction in response to ovalbumin, histamine and acetylcholine. The non-selective NO synthase inhibitor L-NAME partially abolished the effect of Provinol on acetylcholine and ovalbumin-induced but not histamine-induced bronchoconstriction. A similar profile was observed after 14 days' oral administration of Provinol. In conclusion, Provinol inhibited the allergen- and spasmogen-induced contraction of tracheal smooth muscle in ovalbumin-sensitized guinea pigs via a mechanism that was mediated at least partially through the metabolism of NO.