Tumor uptakes and organ distributions of gallium-67 oxalate, ligand bonded to proteins in rodents.

Abstract

Gallium-67 fibrinogen, prepared without stannous tin has been shown by Biogel agarose chromatography, cellulose acetate strip electrophoresis, and coagulability studies done on pure 67Ga-fibrinogen, and on this radiopharmaceutical isolated from rat blood, 12 h and 3 h after injection, to be stable for 3 h. This is the time when most of the tumor uptake of 67Ga occurs as shown by Sephton (1964) and Larson (1978c). In the R3259, large cell sarcoma, in Fisher rats, 67Ga fibrinogen, prepared without tin, has been shown to have significantly higher tumor/blood ratios than 67Ga citrate at 24 h after injection. This is due partly to the higher uptake in the tumor, and partly to the fact that the blood level of 67Ga-fibrinogen drops from 80% of the dose at 12 h after injection to 8% of the dose at 24 h after injection. When prepared with stannous tin, 67Ga-fibrinogen shows significantly higher tumor/organ ratios in the SAI, spindle cell sarcomas in A/J mice only when the amounts of gallium-67 and fibrinogen are restricted. This effect is thought to be similar to the scandium effect of HAYES (1980) as both produce higher excretions from the animals, increased uptake in bone, and both involve loose binding of gallium-67 to protein.