Gallium-67 Localization in Lysosomal-like Granules of Leukemic and Nonleukemic Murine Tissues23

Abstract

We used light and electron microscopic autoradiography to determine the localization of “carrier-free” gallium-67 (⁶⁷Ga) in rat and mouse tissues after its parenteral administration as the citrate. Internal conversion electrons of low energy and Auger electrons produced in ⁶⁷Ga decay permit high resolution autoradiography. More than 70% of the ⁶⁷Ga activity detected in cells of AKR mouse tissues was localized in the cytoplasm. In liver, Kupffer cells and parenchymal cells both contained ⁶⁷Ga. Phagocytic cells of thymus, spleen, and lymph nodes were the most heavily labeled cells in these tissues of both leukemic and nonleukemic AKR mice. Thymic epithelial reticular cells also contained ⁶⁷Ga. A striking concentration of ⁶⁷Ga was observed in the epithelium of renal convoluted tubules. Electron microscopic autoradiography disclosed that in all these cell types ⁶⁷Ga was notably associated with heterogeneous electron-dense cytoplasmic granules bounded by single membranes. Grain counts made from representative electron microscopic autoradiographs showed about 60% of the ⁶⁷Ga radioactivity was associated with these cytoplasmic bodies that are morphologically identified as lysosomes or related particles. This autoradiographic study suggests that the intracellular sites localizing ⁶⁷Ga are lysosomes or places of lysosomal enzymatic activity.