Relaxation of the guinea-pig tracheal chain preparation byN6, 2‘-O-dibutyryl 3’,5‘-cyclic adenosine monophosphate

N 6,2′-O-Dibutyryl 3′,5′-cyclic adenosine monophosphate (dibutyryl 3′,5′-amp), isoprenaline and theophylline relax the guinea-pig tracheal chain preparation; whereas 3′,5′-cyclic adenosine monophosphate (3′,5′-amp) does not. The relaxant effect of isoprenaline, but not that of dibutyryl 3′,5′-amp, was blocked by propranolol. 3′,5′-amp is hydrolyzed rapidly by beef heart phosphodiesterase whereas dibutyryl 3′,5′-amp is not. The presence of equimolar concentrations of dibutyryl 3′,5′-amp does not alter the rate of phosphodiesterase mediated hydrolysis of 3′,5′-amp. These data are consistent with the theories that relaxation of the guinea-pig trachea may be mediated by 3′,5′-amp and that dibutyryl 3′,5′-amp acts by mimicking 3′,5′-amp at its site of action.