A Protein-Binding Assay for Direct Determination of Adenosine 3′,5′-Monophosphate in Amniotic Fluid, Cerebrospinal Fluid, Plasma, and Urine

An adenosine 3',5'-monophosphate (cyclic AMP)-binding protein was isolated from bovine skeletal muscle. This preparation showed maximum binding capacity for cyclic AMP at the physiological pH of amniotic fluid, cerebrospinal fluid, and plasma and had a high association constant of 1.4x10(9) 1/mol. This preparation of binding protein, together with albumin and EDTA in the assay buffer, gave a sensitive and specific competitive protein-binding assay that permitted direct determination of cyclic AMP in the biological fluids mentioned above.