title: Isolation of radioactive iodothyronines for kinetic studies: a comparison of two methods.
abstract: A method based on the principle of gel separation followed by antibody extraction (GSAE) has been developed for isolation of radioactive thyroxine (T4), 3,5,3'-triiodothyronine (T3), 3,3'5'-triiodothyronine (rT3), 3,3'-diiodothyronine (3,3'-T2), 3',5'-diiodothyronine (3',5'-T2) and 3'monoiodothyronine (3'-T1) in serum. This method was used for the estimation of the metabolic clearance rate (MCR( of the iodothyronines using the single injection, non-compartmental approach, and was compared to the conventional trichloroacetic acid precipitation/ethanol extraction (TCA-E) technique. The GSAE method excluded the co-determination of radioactive iodine ad iodoproteins, whereas the co-determination of radiolabelled daughter iodothyronines was found negligible. The relative difference of duplicate estimation of MCR was approximately 10%. Using the TCA-E method for isolation of tracer, the MCR of T4, T3 and rT3 was underestimated to a minor degree (20%), whereas the MCRs of 3,3'-T2, 3'5'-T2 and 3'-T1 were 20-40% of the estimated by the GSAE method. In conclusion the GSAE method was found suitable for kinetic studies of iodothyronines, whereas the TCA-E method cannot be used for turnover studies of 3,3'-T2, 3'5'-T2 or 3'T1.
mesh_terms: D000328:Adult; D000368:Aged; D000918:Antibody Specificity; D011232:Chemical Precipitation; D002850:Chromatography, Gel / Q000379:methods*; D003429:Cross Reactions; D004104:Diiodothyronines / Q000302:isolation & purification; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D013963:Thyroid Hormones / Q000276:immunology / Q000302:isolation & purification*; D013970:Thyronines / Q000302:isolation & purification; D013974:Thyroxine / Q000302:isolation & purification; D014238:Trichloroacetic Acid; D014284:Triiodothyronine / Q000302:isolation & purification
chemical_list: D004104:Diiodothyronines; D007457:Iodine Radioisotopes; D013963:Thyroid Hormones; D013970:Thyronines; D014284:Triiodothyronine; C019017:3'-monoiodothyronine; D014238:Trichloroacetic Acid; D013974:Thyroxine