Studies on the rat liver following iron overload: biochemical studies after iron mobilization

We have characterized the distribution of iron in different organs of the rat, as well as in subcellular fractions of rat liver during iron loading and during physiologic and induced mobilization of iron. Elimination of iron through the bile was also measured. Iron loading was achieved by giving Jectofer injections, and unloading was obtained by weekly phlebotomizations. To study the fate of iron in the lysosomal compartment we have modified the method for the isolation of iron-loaded lysosomes (residual bodies) using Percoll as gradient medium. Thirty per cent of the stored iron was recovered in the liver, and this compartment gradually decreased during unloading. The spleen stored a minor part initially. This part was, however, increased 2 months after the loading was completed. A high concentration of iron was recovered in isolated liver lysosomes. A substantial portion was also found in the microsomal fraction and the ensuing 100,000 x g supernatant. Ultrastructural investigation showed few ferritin or hemosiderin granules in the microsomal fraction. After unloading, the lysosomes evidently decreased in density both in bled and nonbled animals concomitant with a decrease in iron content. In addition to lysosomes, iron was also mobilized from the microsomal fraction. Biliary iron was increased 100 per cent after iron loading and was further enhanced during unloading, in spite of the lowered concentration of iron in the liver. Enzymatic analysis suggested that in the bled animals iron-loaded lysosomes disappeared more rapidly from Kupffer cells than from the parenchymal cells.