1. The ferritin content of iron-overloaded tissues was higher than that of normal tissues. There was also an increased iron content of ferritin extracted from these tissues. 2. In the limited number of tissues that we examined haemosiderin deposition appeared to be greater in the iron-overloaded livers than in the iron-overloaded spleens. 3. Ferritins extracted from iron-overloaded liver, spleen and kidney had similar properties to those extracted from the corresponding normal tissues. 4. Ferritin from iron-overloaded heart had a greater proportion of more basic isoferritins than had ferritin from normal heart. 5. Immunoreactivity to heart and spleen ferritin antibodies, subunit composition, iron content and rate of iron uptake of both unfractionated ferritin and isoferritin fractions separated by ion exchange chromatography were related to the isoelectric point.
1. Ferritin has been partially purified from the serum of patients with idiopathic haemochromatosis. 2. Incubation with neuraminidase of this partially purified serum ferritin eliminated much of the microheterogeneity of the protein so that only ferritin of isoelectric point approximately 5·8 was present. 3. There was no change in the total amount of ferritin present (measured immunologically) or in the percentage of ferritin binding to concanavalin A. 4. Incubation of liver, spleen or heart ferritin with neuraminidase did not change the isoelectric focusing patterns.
1. A high proportion of the ferritin in normal serum binds to concanavalin A. Binding is prevented by the addition of α-d-methylglucoside to the reaction mixture. 2. Ferritin in extracts of normal heart, liver and spleen or serum ferritin from patients with massive hepatic necrosis does not bind to concanavalin A. 3. Isoelectric focusing of preparations of serum ferritin from patients with primary haemochromatosis shows that the ferritin fraction binding to concanavalin A consists, predominantly, of the more acidic isoferritins. 4. These findings suggest that carbohydrate residues may be added to ferritin during its secretion into the plasma. Glycosylation may account for the heterogeneity of serum ferritin on isoelectric focusing. 5. Direct release of intracellular ferritin from damaged tissue may be indicated by an increase in the proportion of circulating ferritin which does not bind to concanavalin A. Such an increase has been found in sera from patients with iron overload.