The use of iodinated tracers for a sensitive radioimmunoassay of 13,14-dihydro-15-ketoprostaglandin Falpha.

Radioimmunoassay of 13,14-dihydro-15-ketoprostaglandin Falpha is reported using various 125I-labelled derivatives. The apparent association constants of the antiserum for iodinated tracers are higher than with the homologous hapten. In spite of this, the high specific activities of iodinated tracers (2000 Ci/mmol) allow a 3-fold increase in the sensitivity of the assay when compared with the tritiated derivative. Human plasma levels of 13,14-dihydro-15-ketoprostaglandin Falpha reported (25+/-6 pg/ml) are lower than those previously found by radioimmunoassay, and no sexual difference was found.