⁶⁷Ga Binding to Human Serum Proteins and Tumor Components

⁶⁷Ga is known to concentrate in a variety of malignant tumors. Immunoelectrophoresis combined with autoradiography of human serum incubated with ⁶⁷Ga showed that the radionuclide is associated with transferrin, apart from a weak binding to β-lipoprotein. The thermodynamic constant for gallium was estimated and indicated that gallium citrate in the presence of serum proteins occurred in a colloid form bound to transferrin.

Ultracentrifugation of tumor homogenates obtained from patients who had received i.v. injections of ⁶⁷Ga citrate for scintigraphy demonstrated that ⁶⁷Ga is preferentially bound to proteins in the nuclei fraction. Acrylamide gel electrophoresis of extracts of cancer tissue indicated that intracellular ⁶⁷Ga is associated mainly with a fast-migrating substance, perhaps a protein, with a molecular weight lower than that of ferritin.