A batch procedure for the assay of cyclic nucleotide phosphodiesterase.

A procedure for the assay of cyclic nucleotide phosphodiesterase is described in which labeled cyclic nucleotide is separated from labeled nucleoside by the batchwise addition of ethanolic slurries of Dowex 2 fluoride. Under the conditions described there is no detectable adsorption of nucleoside by the anion exchanger, which removes more than 95% of the tritium in boiled samples of 8-³H]cAMP or 8-³H]cGMP. Linear time courses and enzyme vs activity relationships are described for 10^?3 and 10^?7m cAMP and 10^?4m cGMP. The method is limited by interference by neutral salts and by the enzymatic conversion of adenosine into inosine.