Use of protein A-positive Staphylococci as adsorbent in a radioimmunoassay for cyclic AMP and cyclic GMP

Abstract

A reproducible (SD<4%), sensitive (in the 5 to 50 fmoles range) and inexpensive radioimmunoassay has been set up for the quantitation of cyclic AMP and cyclic GMP based on acetylation or succinylation of the test sample. Separation of antibody-bound from free ligand was achieved by adsorption to formalinized protein A-positive Staphylococci of the Cowan 1 strain. The quantity of adsorbent (5% suspension) needed per 300 μl of antiserum (diluted 24 × 10⁴) was 10 μl. The blank value was below 2% and separation could be run at room temperature or at 4°C as convenient. The acetylation or succinylation procedure of the sample totally eliminated interference of test sample immunoglobulins with antiserum binding to the adsorbent.

Key Words:

• acetylation
• cyclic nucleotide assay
• Cowan 1 Staphylococcus aureus
• reproducible separation
• succinylation
• ultrasensitive