Saturation of anti cyclic nucleotides antibodies by endogenous cyclic nucleotides.

Rabbits immunized against cyclic AMP or cyclic GMP produce antibodies which are fully saturated by their respective endogenous cyclic nucleotides. This was proved a) in comparing radioimmunological measurements of cyclic nucleotides in antiserum and the binding site concentration determined by equilibrium dialysis, b) in showing the ineffectiveness of serum phosphodiesterase to hydrolyze the cyclic AMP present in the anti-cyclic AMP antiserum. Immunological and radioimmunological implications of this phenomenon are discussed.