A separation method for the assay of adenylylcyclase, intracellular cyclic AMP, and cyclic-AMP phosphodiesterase using tritium-labeled substrates

A method for the separation of cyclic AMP from adenosine and polyvalent adenine nucleotides is described. The method consists of the sequential elution of adenosine and cyclic AMP from a single column of acidic aluminum oxide (alumina) with dilute hydrochloric acid and ammonium acetate. Adenosine, adenine, xanthine, and hypoxanthine are rapidly eluted with the application of 0.005 n hydrochloric acid while cyclic AMP remains adsorbed to the alumina. A subsequent application of 0.1 m ammonium acetate elutes more than 90% of the cyclic AMP. Under these conditions, polyvalent nucleotides (AMP, ADP, and ATP) remain adsorbed to the alumina. The method permits the measurement of adenylylcyclase activity using [ 3H]ATP as the labeled substrate. The same technique can be used to measure the accumulation of cyclic AMP in intact cells after labeling the ATP pool with [ 3H]adenine. With slight modification, the technique can be used to measure the activity of cyclic-AMP phosphodiesterase using [ 3H]cyclic AMP as the substrate. The proposed technique provides rapid, highly reproducible assays using inexpensive, disposable columns.