The analysis and assay of cyclic nucleotide phosphodiesterase isoenzyme activity

Greater knowledge over the past decade on the biochemical properties, as well as the identification of specific pharmacological tools has led to a marked improvement in the methods employed for the analysis and assay of PDE isoenzymes. A major message has been the marked species and tissue-dependent variation in the distribution of the various isoenzymes and their subtypes. This has great implications not only in terms of extrapolating animal data to the human situation, but also from one tissue to another. Thus, it is critical, in particular for drug discovery efforts, to characterize human PDEs in the relevant tissue. Molecular cloning is probably the best and most direct route to achieve this objective since access to disease-free human tissue is heavily limited. Alternatively, well-characterized animal tissues showing PDE and pharmacological profiles similar to human tissues may be utilized. The methods described in this chapter have been successfully applied to study to the biochemistry and pharmacology of PDEs in both animal and human tissues, and in the discovery of novel selective inhibitors for these proteins.