Synthesis of¹²⁵I Monolabelled 3, 5, 3′-Triiodothyronine and Thyroxine of Maximum Specific Activity for Radioimmunoassay

Abstract

AbstractA chloramine T technique for the synthesis of monoiodinated 3,5,3′-125I-T3 and 125I-T4 is described using diiodothyronine and triiodothyronine as 125I-acceptors. Specific activities in the order of 3000 mCi/mg T3 are routinely obtained, i.e. approaching the theoretical maximum value. With these high specific activity products, which are at least 10 times higher than any previously described, it becomes possible to determine free T3 (and T4) directly in ultrafiltrates or dialysates of plasma samples.Key Words: Free T3free T4iodinationradioimmunoassaySephadex-adsorption-chromatographyspecific activitythyroxinetriiodothyronine