Cyclic AMP compartments and signaling specificity: role of cyclic nucleotide phosphodiesterases.

### Introduction The concept that cAMP has restricted access to different pools of intracellular effectors was articulated more than 30 years ago. Observations made by [Corbin et al. (1977)][1] demonstrated that the two isoenzymes of the major intracellular cAMP target, PKA I and II, are located in