Studies on the rat liver following iron overload. Electron probe x-ray microanalysis of acid phosphatase and iron

Previous electron-microscopic studies on the liver have shown that following excessive administration of iron to experimental animals, small particles believed to represent ferritin and/or hemosiderin (electron-dense iron-containing particles [IPs]) accumulate in membrane-bound bodies--many with a lysosome-like structure--in liver parenchymal and Kupffer cells. Further identification of the IP-containing bodies has been facilitated by the application of histochemical techniques for the demonstration of acid phosphatase. The results have shown that reaction product was deposited over organelles similar in appearance to the IP-containing ones, indicating that they were lysosomes. However, the granular nature of the reaction product makes it difficult or impossible to decide whether IPs are present simultaneously with reaction product in the organelle. In order to clarify this qualitative aspect, x-ray microanalysis has been utilized to identify iron and lead (reaction product) in the various structures thought to represent lysosomes. The results indicate that all IP-containing bodies also show the presence of reaction product, and thus can be regarded as lysosomes. However, in the parenchymal cells there may exist a small population of iron-deficient lysosomes (only lead could be shown). The latter may correspond to "primary lysosomes."