Autoradiographic detection of radiolabeled dPG35S amine in organs and tissues. (a) Semiquantitative micro imager analysis detected different amounts of dPG35S amine in mouse organs, decreasing from the kidney over the liver and the spleen to the heart one hour after intravenous injection (top panel: counting rates with regions of interest (indicated by red lines); bottom panel: combination of optical image and counting rates). (b) Single organ autoradiography of mouse kidney (left panel) and spleen sections (right panel) on X-ray film following dPG35S amine application identified distribution patterns of the radiolabeled NP in accordance with organ specific functional structure. In the kidney, NP were localized within the renal cortex (outer rim) whereas in the spleen they were clearly associated with the red pulp but not within lymphoid follicles (spared dots). (c) Light microscopic autoradiography with numerous radioactive decay-induced signals over Kupffer cells (arrows) in the liver of a mouse (left panel). Signals were sparse in adjacent hepatocytes with larger, more round nuclei. No signals were observed when unlabeled dPGS amine was used under otherwise identical experimental conditions (right panel). Hematoxylin and eosin-stained FFPE tissue sections.