Accumulation of radioisotopes with tumor affinity. I. Uptake and excretion of 67Ga-citrate in malignant tumors and normal cells

Using in vivo and in vitro experimental models, the uptake and excretion of 67Ga-citrate in tumor cells and normal cells were studied. The time-lapse accumulation of 67Ga in the tumor of rats bearing Yoshida sarcoma reached its peak 24 h after the administration of 67Ga and gradually decreased thereafter. However, the excretion of 67Ga from the tumor was less than that from normal lung. For culture cells in vitro, the uptake of 67Ga increased with lapse of contact time between 67Ga and the cells, but there was no distinct difference between the results of tumor cells and normal skin fibroblasts. The excretion of 67Ga from the cells tended to decrease with prolongation of the contact time, the excretion from tumor cell being only about 10% after a contact time of 24 h. This indicated a significant delay in excretion in comparison with that of normal skin fibroblasts. This delay in the excretion of 67Ga may be an important factor in the tumor accumulation of 67Ga.