Transport of ferritin from Kupffer cells to liver parenchymal cells. Morphological and immunocytochemical observations

In attempting to determine the pathway of ferritin from Kupffer cells to liver parenchymal cells, anionic iron colloid particles of a ferric hydroxide-potassium polyvinyl sulfate complex (Fe-PVS) were injected intravenously into blood-depleted anemic rats. After iron loading, the process of ferritin formation and the daily change in the latter's distribution in the liver were studied by ultrastructural-immunocytochemical techniques. Three days after Fe-PVS injection, a mass of reaction products of ferritin was found in Kupffer cells, though not in the sinusoidal endothelial or parenchymal cells. Four days post-Fe-PVS injection, however, reaction products in Kupffer cells disappeared, while appearing in parenchymal cells. Observations at 3.5 days after the injection revealed heavy deposition of reaction products in the sinusoid and Disse's spaces as well. Electron microscopic observation of tissue sections treated with bismuth subnitrate taken at this stage revealed diffuse dispersion of ferritin particles in the cytoplasmic matrix of parenchymal cells as well as in the sinusoid and Disse's spaces. Ferritin particles were not found in the coated pits and vesicles of the Kupffer cells and parenchymal cells. Four days after injection, ferritin particles were found in clusters in the cytoplasm in the parenchymal cells and also in their lysosomal bodies. The results indicate that ferritin synthesized in Kupffer cells is released into sinusoidal and Disse's spaces and then accumulated in parenchymal cells.