The Preparation of132I and131I Labelled Human Serum Albumin for Clinical Tracer Studies

In a report which predicted the availability of fission product 132Te (Winsche, Stang and Tucker, 1951) it was suggested that its daughter product, 132I, might be of value in the diagnosis and treatment of thyroid disorders. It soon became apparent that 132I would be valuable for many other clinical applications, such as haemodynamic studies and plasma volume measurements, since the short half-life of 2·26 hours (Emery and Veall, 1954) would permit the administration of comparatively large tracer doses without appreciable radiation hazards to the patient (see note A below); and measurements could be repeated at frequent intervals without interference from residual activity. For such applications it was first necessary to develop a method whereby the isotope could be prepared in the form of sterile iodinated human serum albumin, and which unlike the procedures currently employed for 131I, could be carried out in an hour or less. The following procedure, which was based on that employed by Francis, Mulligan and Wormall (1951), meets these requirements and is of course equally applicable to 131I. (All chemicals of analytical reagent grade.) Ammonia solution N (20:1 dilution of 0·88 ammonia solution). Hydrochloric acid N (10:1 dilution of concentrated HC1). N/50 sodium sulphite solution (125:1 dilution of saturated Na2SO3 solution, pH7). (The above solutions are freshly prepared using sterile pyrogen free water.) Potassium iodide solution, 2 mg/ml. Potassium iodate solution, 1 mg/ml. Potassium iodide solution 20 per cent w/v approx. Hydroxylamine sulphate N/10.