Dissociation of magnitude of relaxation from cyclic AMP levels in rabbit urinary bladder smooth muscles.

The effects of forskolin and isoproterenol on contractile force and cyclic AMP levels were compared in smooth muscle strips from rabbit urinary bladder dome. Both of forskolin and isoproterenol produced the time- and the dose-dependent relaxation and the time- and the dose-dependent increases in cAMP levels. The relaxant response to forskolin caused more slowly than that to isoproterenol. The two agents caused almost the same relaxant responses at same concentration. However, cAMP levels induced by forskolin was much more than those induced by isoproterenol. These results that amounts of cAMP in urinary bladder don't correlate with the relaxation responses in urinary bladder smooth muscle strips suggest that some forms of functional compartmentalization of cAMP may exist in the urinary bladder.