COMPARISON OF THE METHODS FOR TISSUE TRIIODOTHYRONINE (T3) EXTRACTION AND SUBSEQUENT RADIOIMMUNOASSAY

Abstract

ABSTRACT Although there have been various reports on tissue T3 concentration, the examination of the quality of radioimmunoassay has not been available. In the present study, we tried to determine whether the available methods for T3 extraction are adequate for the various methods of T3 radioimmunoassays used. T3 was extracted from liver by ethanol extraction or by acid butanol extraction (Flock's method) and the extract was applied to radioimmunoassay either by Seralute T3 column, ANS-double antibody or the ANS-charcoal method. The values of T3 were compared with those obtained by isotope-equilibration method. The dilution curve of ethanol extract was not parallel with that of the standard in ANS-charcoal or ANS-double antibody technique. When the extract was tested by Seralute method, the dilution curve was parallel to the standard, whereas the T3 value obtained with this method was two-fold higher than that with the isotope equilibration technique. The analysis of the ethanol extract suggested that the lipid extracted by ethanol interfered with the assay. The acid butanol extract when tested either by the ANS-double antibody or Seralute method, showed parallelism to the standard curve and gave T3 values almost identical with those by the isotope-equilibration method. When tested by ANS-charcoal method, the dilution curve of the acid butanol extract was not parallel to the standard. Thus, to obtain reliable results, tissue extraction by Flock's method and subsequent T3 radioimmunoassay by either ANS-double antibody or Seralute T3 method are recommended.