Interaction of albumin, transferrin, and human serum with indium-113 m complexes of ethylenediaminetetraacetic acid, penicillamine, and related compounds.

Abstract

The interaction between the indium complexes and human serum proteins has been investigated by electrophoresis and gel filtration. Excess indium above serum transferrin level bound to albumin and α1-globulins besides to transferrin. The sulfhydryl-containing ligands and ethylenediaminetetraacetic acid (EDTA) prevented the indium binding by albumin, in contrast with common amino acids. The indium complexes of penicillamine, 2, 3-dithiopropanol (BAL), and EDTA resist the transfer of indium from the complexes to transferrin and the ability is related to the stability of the complexes, and to the molecular form and size of the ligands. Thioglycolic acid which prevents the hydrolysis of indium and forms the indium-transferrin-thioglycolate ternary complex, is available for the effective preparation of 113mIn-or 111In-transferrin. The binding-affinity of In (III) to ovotransferrin was approximately equal to that of Fe (III). The indium complex of EDTA was present in the form of the dimer at the physiological pH, as well as the ferric complex. On the basis of these results, the usefulness of the inert indium complexes of EDTA, penicillamine, BAL, and the disulfhydryl-containing peptides as imaging agents, has been discussed.