Hepatic sinusoidal cells in iron overload. Ultrastructural observations.

The ultrastructure of sinusoidal cells was studied in 18 liver biopsies from patients with homozygous beta-thalassemia. No conspicuous iron was seen in sinusoidal cells from biopsies obtained before transfusion therapy was initiated, although electron-dense iron was present in some parenchymal cells. Biopsies following the high transfusion regime showed progressive increase in the size and number of iron-containing lysosomes in both parenchymal and sinusoidal cells. This study confirms the view that transfusional iron is largely segregated in reticuloendothelial cells. Examination of stained and unstained sections showed the Kupffer cells and endothelial cells had different types of iron-containing lysosome that were also dissimilar from most iron-containing lysosomes seen in hepatocytes. The described cell-specific morphological features of the lysosomes facilitate the identification of various cells during iron overload. The importance of phagocytic sinusoidal cells during chronic iron overload is stressed.