A Radioimmunoassay for cyclic AMP (cAMP) Obtained by Acetylation of Both Unlabeled and Labeled (³H‐cAMP) Ligand, or of Unlabeled Ligand only

Abstract

A sensitive radioimmunoassay (limit of detection 7 +/- 1 fmol per tube) for cyclic AMP (cAMP) based on acetylation of both 3H-cAMP and unlabeled ligand was developed. Rabbit anti-cAMP antibodies had an apparent Ka for the acetylated ligand of 2 x 10(10) l/mol. When the unlabeled ligand only was acetylated an increased sensitivity was obtained without loss of specificity.