Bronchoprotective effects of KF-19514 and cilostazol in guinea pigs in vivo

Abstract

It has been shown that inhibitors of cyclic nucleotide phosphodiesterase III and IV have a bronchodilator effect. We compared the effects of a selective phosphodiesterase III inhibitor, 6-[4-(1-cyclohexyl-1 H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1 H)-quinolinone (cilostazol) and a phosphodiesterase I/IV inhibitor, 5-phenyl-3-(3-pyridil) methyl-3 H-imidazo[4,5- c][1,8]naphthyridin-4(5 H)-one (KF-19514) on antigen- and histamine-induced bronchoconstriction in guinea pigs in vivo. Intravenous administration of cilostazol and KF-19514 inhibited histamine- and antigen-induced bronchoconstriction in a dose-dependent manner. When assessing the resulting ED 50 values, the activity of KF-19514 against antigen-induced bronchoconstriction was stronger than its antagonism of histamine-induced bronchoconstriction (0.004 vs. 0.056 mg/kg), while those of cilostazol were contrary (0.835 vs. 0.031 mg/kg). These results suggest that although both inhibitors of phosphodiesterase III and phosphodiesterase IV have a bronchodilator or bronchoprotective effect, phosphodiesterase IV inhibitors such as KF-19514 may be more useful for asthma treatment because KF-19514 had an anti-allergic effect in addition to the functional bronchodilator activity.