[Effects of a cyclic nucleotide phosphodiesterase isoenzyme type III inhibitor, SDZ MKS 492 on airway responsiveness in beagles].

To elucidate the effects of cyclic nucleotide phosphodiesterase (PDE) isoenzyme inhibition on airway responsiveness, we studied the effects of a selective PDE isoenzyme type III inhibitor, SDZ MKS 492, on airway responsiveness to inhaled methacholine (Mch) in 6 beagles. Base-line respiratory resistance and airway responsiveness to Mch were determined by modified Astograph (7 Hz oscillation method). SDZ MKS 492 (1.0 mg/kg, 0.3 mg/kg or 0.1 mg/kg) was orally administered 1 hr prior to the determination of airway responsiveness at intervals of one week. Base-line respiratory resistance was decreased in a dose-dependent manner by SDZ MKS 492. SDZ MKS 492 significantly decreased airway responsiveness to Mch (log D min) in a dose-dependent manner, and the airway responsiveness (log PD2.0 Mch) was significantly decreased by 1.0 mg/kg of SDZ MKS 492. These results indicate that selective inhibition of PDE isoenzyme type III results in a decrease in respiratory resistance and airway responsiveness.