The purification and characterization of radiolabelled parathyroid hormone for radioimmunoassay.
An improved method for the purification of 125I-labelled PTH is presented. Following iodination of the hormone by the chloramine-T method, the reaction mixture is transferred directly to a 0.9 x 9 cm column of carboxymethyl-cellulose. Two major peaks emerge with the ammonium acetate gradient. Peak I represents labelled intact bPTH, Mr 9600, of good quality, i.e. a high B0 and a low NSB in the radioimmunoassay. Peak II, Mr approximately 12000-18000, gives a high B0, but also a high NSB and is less suitable for RIA. Peak II is not the result of iodination damage, as it is also present in the unlabelled PTH (Inolex); it is suggested that it represents either a pre-prohormone or an aggregate of PTH. The label produced is usable for up to 3 months. Trasylol and benzamidine protect the label against proteolytic degradation equally well; the latter, however, is considerably cheaper.
D001550:Benzamidines; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004355:Drug Stability; D007457:Iodine Radioisotopes; D007553:Isotope Labeling; D010281:Parathyroid Hormone / Q000302:isolation & purification*; D011863:Radioimmunoassay
D001550:Benzamidines; D007457:Iodine Radioisotopes; D010281:Parathyroid Hormone