Altered biodistribution of radiogallium following BCG treatment in mice

Abstract

Abstract A mouse animal model has been used in this study which was prompted by clinical observations that 67 Ga-citrate scintigraphs of patients with multi-system melanoma who had been treated with BCG revealed unusually high blood concentrations of the radiotracer, abnormal diffuse pulmonary localization and increased uptake at sites not corresponding with clinical evidence of metastases. Groups of mice were immunized by a series of intradermal injection of BCG. Tissue distribution studies were performed 48 h after i.v. injection of 67 Ga-citrate. These same tissues were also examined histopathologically. Increased uptake of radiogallium was seen in the liver, lungs, spleen, kidneys and blood of the BCG-treated mice when compared to normal controls. A close correlation was seen between the incidence of increased radiogallium concentrations and the presence of microscopically visible lesions in each of the tissue samples. Autoradiography of liver sections from BCG-treated mice injected with 67 Ga-citrate indicated that the radioactivity was localized to a large extent, at sites of BCG induced granuloma. 67 Ga was shown to be taken up significantly by live BCG cells in in vitro incubation but little or no incorporation occurred with heat-killed BCG.