A Radioimmunoassay for Measurement of 3,3′, 5′-Triiodothyronine (Reverse T₃)

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Abstract

A highly specific antiserum to 3,3′,5′-triiodothyronine (reverse T3, rT3) was prepared by immunization of rabbits with D,L-rT3-human serum albumin conjugate. Of the various thyroid hormone derivatives tested, only 3,3′-diiodothyronine (3,3′-T2) cross-reacted significantly (10%) with rT3-binding sites on the antiserum, while thyroxine (T4) and triiodothyronine (T3) cross-reacted by less than 0.1%. The antiserum was used in a simple, sensitive, precise, and reproducible radioimmunoassay (RIA) for measurement of rT3 in ethanolic extracts of serum. The dose-response curves of inhibition of the binding of [125I]rT3 to antibody obtained by serial dilutions of serum extracts were essentially parallel to the standard assay curve. Recovery of nonradioactive rT3 added to serum before extraction averaged 93%.

Authors

Inder J. Chopra