A Rapid and Economical Method of Preparing Radioiodinated Cyclic Nucleotide Derivatives for use in Radioimmunoassays

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Abstract
2′-0-succinyladenosine 3′:5′-cyclic monophosphate tyrosyl methyl ester (ScAMP-TME) and 2′-0-succinylguanosine 3′:5′-cyclic monophosphate tyrosyl methyl ester (ScGMP-TME) were radioiodinated using chloramine T and Na125 I. The resulting radiolabeled cyclic nucleotide derivatives, ScAMP-125 I-TME and ScGMP-125 I-TME, were subsequently purified by reverse-phase chromatography on Sep-Pak C18 cartridges (Waters Associates, Milford, MA) and tested as tracers in sensitive radioimmunoassays for cAMP and cGMP, respectively. Purified ScAMP-125 I-TME and ScGMP-125 I-TME functioned in the respective radioimmunoassays for up to 12 weeks when suspended in a 1:1 (v:v) mixture of n-propanol and 20 mM sodium acetate, pH 6.0. Thus, this purification method enables rapid and economical preparation of tracers for cyclic nucleotide radioimmunoassays. Furthermore, our findings suggest that reverse-phase chromatography may be applicable to the purification of other small polar molecules to which tyrosyl groups have been added for the purpose of radioiodination.