67Ga accumulation and heparan sulfate metabolism in lysosomes

67Ga incorporation in the mitochondrial-lysosomal (Mt-Ly) fraction of rat liver increased sharply from 1 to 24 h after 67Ga IV injection, whereas that in the 105,000 g supernatant fraction decreased sharply from 6 to 48 h. Further, when 14C-labeled heparan sulfate (HS: biosynthesized by injection of [1-14C] glucosamine into a rat) was injected intravenously into a rat treated with Triton WR-1339, and the liver was isolated and fractionated, the radioactivity of 14C was concentrated in the lysosomal fraction. The effect of HS on 67Ga uptake in normal rat liver was also studied. On administration of 67Ga-HS complex, the peak uptake of administered radioactivity of 67Ga in rat liver occurred sooner than after the injection of 67Ga alone. The change was greatest in the Mt-Ly fraction among the subcellular fractions. Moreover, the 67Ga uptake in rat liver increased with increasing doses of HS. These results suggest that administered 67Ga may be bound to HS and that the concentration of 67Ga in lysosomes may be related to the in vivo metabolism of HS.