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

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Abstract
Although there have been various reports on tissue T3 [triiodothyronine] concentration, an examination of radioimmunoassay quality has not been available. Whether the available methods for T3 extraction are adequate for the various methods of T3 radioimmunoassays used was determined. T3 was extracted from [rat] liver by ethanol extraction or by acid butanol extraction (Flock''s method). The extract was applied to radioimmunoassay either by the Seralute T3 column, ANS[8 anilino-naphthalene-sulfonic acid]-double antibody or the ANS-charcoal method. The T3 values were compared with those obtained by isotope-equilibration method. The dilution curve of ethanol extract was not parallel with that of the standard in the ANS-charcoal or ANS-double antibody technique. When the extract was tested by the Seralute method, the dilution curve was parallel to the standard, whereas the T3 value obtained with this method was 2-fold higher than that with the isotope equilibration technique. 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 the Seralute method, showed parallelism to the standard curve and gave T3 values almost identical with those by the isotope-equilibration method. When tested by the ANS-charcoal method, the dilution curve of the acid butanol extract was not parallel to the standard. To obtain reliable results, tissue extraction by Flock''s method and subsequent T3 radioimmunoassay by either ANS-double antibody or the Seralute T3 method are recommended.