Enzyme immunoassays for the estimation of adenosine 3',5' cyclic monophosphate and guanosine 3',5' cyclic monophosphate in biological fluids.

Simple, rapid and sensitive competitive enzyme immunoassays for the estimation of adenosine 3',5' cyclic monophosphate (cAMP) and guanosine 3',5' cyclic monophosphate (cGMP) in human plasma and urine are described. Specific antisera to each nucleotide were raised in rabbits by immunization with succinyl cyclic nucleotide--human serum albumin conjugates. For the assay, specific antibodies were incubated with a mixture of succinyl cyclic nucleotide labelled with horseradish peroxidase together with unlabelled standard or sample. The antibody-bound enzyme conjugate was separated from free hapten by anti-rabbit (IgG) sera immobilized to a microtitre plate. Activity of the bound enzyme conjugate was determined with tetramethylbenzidine. The assays were capable of detecting levels as low as 2 fmol of cAMP and cGMP. Good correlations were obtained between values generated by enzyme immunoassay and radioimmunoassay.