Assessment of phosphodiesterase isozyme contribution in cell and tissue extracts.

Cyclic nucleotide phosphodiesterases (PDEs), which are ubiquitously distributed in mammalian tissues, play a major role in cell signaling by hydrolyzing cyclic adenosine 3',5'-monophosphate and cyclic guanosine 3',5'-monophosphate. Owing to their diversity, which allows specific distribution at the cellular and subcellular level, PDEs can selectively regulate various cellular functions. We present here a convenient and sensitive radioenzymatic assay for characterizing and determining the contribution of the various PDE families in cell and tissue extracts. This assay is based on the knowledge and use of chosen PDE family-specific inhibitors in order to determine the distinct PDE isozyme contribution in the overall cyclic nucleotide hydrolyzing activity. It can be used to characterize total, cytosolic, and membrane-associated PDE activities, as well as PDEs associated with purified subcellular structures. This approach is useful for comparing data of control and treated extracts and is therefore quite valuable for viewing the PDE status in different physiopathological conditions.