Abstract
5,7,2′,5′-Acetoxy-4-phenylcoumarin relaxed normal isolated guinea pig trachea and those contracted with small doses of carbachol. While β-adrenoceptors are not involved in the relaxant effect, inhibition of Ca2+-influx may be an important mechanism since the degree of relaxation is inversely proportional to the Ca2+ concentration in the bath and since the cumulative concentration-effect curves to Ca2+ and K+ are antagonized by the coumarin. The compound also inhibited leukotriene-mediated arachidonic acid-induced contraction of indomethacin-treated trachea, but was inactive in antagonising ovalbumin-induced contractions of sensitized trachea.
