Chromatographic Behaviour of Human Albumin labelled with Iodine-131

Abstract

THE in vivo behaviour of plasma proteins labelled with iodine-131 prepared by methods developed in this laboratory^1,2 is almost identical with that of the corresponding proteins labelled with carbon-14 by the biosynthetic procedure^3,4. Human albumin preparations iodinated by these methods have a chromatographic distribution similar to that of unlabelled albumin when analysed on anion exchange columns of diethylaminoethyl cellulose (Fig. 1). Similar results have been obtained on cation exchange columns of carboxymethyl cellulose. On the other hand, commercially iodinated human albumin (Abbotts, Chicago), which has been extensively used in clinical studies of albumin turnover, has recently been shown to have a chromatographic distribution markedly different from native albumin⁵. It is now recognized that preparations of protein labelled with iodine-131 may be adversely affected by a variety of factors, including the method of fractionation, the technique of iodination¹, preliminary heat treatment of the protein⁶ and self-irradiation⁷. Investigation of these variables has shown that by far the greatest changes in chromatographic behaviour of albumin labelled with iodine-131 result from self-irradiation.