Radiation effect on 67Ga retention and distribution in mouse tissues

We have studied the effect of external x irradiation on the whole-body retention and tissue distribution of gallium-67 (67Ga) in mice over a period of 20 days. Adult male C57BL/6 Cum mice were injected intraperitoneally with 5 μCi 67Ga 24 hr before, immediately before, immediately after, or 24 hr after whole-body x-ray exposure to 450 R. Control mice received 67Ga injections and sham irradiation. Increased excretion and reduced soft-tissue concentrations of 67Ga occurred in irradiated mice. The greatest effect was observed when the radionuclide was injected 24 hr after irradiation and assayed 24 hr later. An analysis of variance of the retention data showed that the differences between the groups were significant at the 99 percent confidence level. Exponential least-squares analysis of whole-body counting results revealed three compartments in the biological retention data. The long-lived compartment possibly corresponds to 67Ga bound relatively tightly in certain body tissues and lost slowly. The two remaining compartments have been tentatively identified as circulating unbound 67Ga that is lost rapidly and circulating bound 67Ga that is lost less rapidly