Comparison of assay procedures for solubilized thyroid hormone receptor

Seven procedures for the assay of thyroid hormone receptor were compared. Receptors from rat liver nuclei were incubated with [125I] triiodothyronine (T3), and the hormone bound to the receptors was separated by the different methods and its radioactivity was counted. Column chromatography on Sephadex G-25, filtration on nitrocellulose membranes, glass filters, or diethylaminoethyl cellulose disks, and vortex/centrifugation with use of hydroxyapatite, Dowex AG 1 x 8 resin, or a mixture of charcoal and dextran were used. Filtration on a nitrocellulose membrane was the most sensitive and accurate method. The use of Dowex AG 1 x 8 was the easiest. Filtration on a glass filter was the best when samples were particulate.