[42] Iodinated derivatives as tracers for eicosanoid radioimmunoassays

Publisher Summary This chapter discusses the use of radioiodinated derivatives in developing sensitive and reliable radioimmunoassays (RIAs) that could be applied to any eicosanoid. All the eicosanoids have a free carboxyl group. This acidic function has been used for the formation of a peptide bound either with the free amino groups of the antigenic carrier for the preparation of the immunogen or with the free amino group of a substance that can be iodinated. The strategy is to select a substance that on the one hand had a low molecular weight to preserve the immunological recognition of the hapten by the antibody site, and on the other hand can be easily iodihated. Three compounds are tested: tyrosyl methylester, tyramine, and histamine. The [ 125 I]histamine derivatives are readily prepared by the iodogen procedure, and the introduction of purification of tracers on HPLC improves their immunostability and reduces the frequency of labeling. The increase of sensitivity obtained with the iodinated tracers reduces the volume of biological sample used and opens new possibilities for investigation.