title: Critical analysis of [131I]- and [125I]human thyroglobulin labels for radioimmunoassay use.
abstract: [125I]- and [131I]thyroglobulin (Tg) tracers obtained by two different oxidation methods, chloramine-T (Chl-T) and lactoperoxidase (LP-ase), were analyzed to assess their suitability in the development of a RIA. Pairs of tracers which were prepared on a single day using these methods with a single source of 131I and 125I were compared. The following conclusions were reached. 1) Both 131I and 125I isotopes, using CHl-T or LP-ase oxidants, produce suitable tracers. 2) [131I]Tg can be used repeatedly for 2 weeks without repurification. 3) [125I]Tg, in contrast, has to be rechromatographed weekly on Sephadex G-200 to maintain assay sensitivity and adequate maximal binding. 4) Under these conditions, 2- or 9-day tracers with either isotope using Chl-T or LP-ase give similar Tg determinations in the serum. 5) The LP-ase-chromatographed 125I tracer seems to lead to higher maximal binding in the assay than the Chl-T-repurified tracer.
mesh_terms: D002700:Chloramines; D004355:Drug Stability; D006801:Humans; D007457:Iodine Radioisotopes; D007553:Isotope Labeling / Q000379:methods*; D007784:Lactoperoxidase; D010084:Oxidation-Reduction; D011863:Radioimmunoassay; D013954:Thyroglobulin / Q000097:blood / Q000276:immunology; D014105:Tosyl Compounds
chemical_list: D002700:Chloramines; D007457:Iodine Radioisotopes; D014105:Tosyl Compounds; C016300:chloramine-T; D013954:Thyroglobulin; D007784:Lactoperoxidase