Solid phase radioimmunoassay for cyclic AMP using staphylococcal protein A-antibody adsorbent

Area of Science:

• Biochemistry
• Immunology
• Analytical Chemistry

Background:

• Cyclic adenosine monophosphate (cAMP) is a crucial second messenger involved in various cellular processes.
• Accurate quantification of cAMP levels is essential for understanding cellular signaling pathways.
• Existing radioimmunoassay methods for cAMP have limitations in sensitivity or complexity.

Purpose of the Study:

• To develop a sensitive and specific radioimmunoassay for cyclic adenosine monophosphate (cAMP).
• To utilize protein A-containing staphylococci as an immunoabsorbent for efficient separation.
• To evaluate the performance of the developed assay compared to established methods.

Main Methods:

• A radioimmunoassay was established using rabbit antiserum against a 2'-O-succinyl cAMP derivative.
• Protein A-containing staphylococci (Cowan I) were coated with antibodies and used as an immunoabsorbent.
• Separation of bound and free labeled antigen was achieved by centrifugation after incubation with [125I]-labeled cAMP derivative.

Main Results:

• The developed radioimmunoassay demonstrated high sensitivity, with 50% depression of zero dose binding at 15-16 femtomoles of acetylated cAMP.
• Acetylation prior to the assay increased sensitivity approximately 80-fold.
• The assay exhibited very low cross-reactivity with structurally related nucleotides like cyclic GMP and ATP.

Conclusions:

• The protein A-staphylococci based radioimmunoassay provides a sensitive and specific method for quantifying cAMP.
• This technique offers an attractive alternative to traditional methods like polyethylenglycol precipitation or second antibody assays.
• The assay's high sensitivity and specificity make it valuable for various research applications in cell signaling.