Rat ferritin isoproteins and their response to iron administration in a series of hepatic tumors and in normal and regenerating liver.

Ferritin was isolated from six Morris hepatomas with growth rates ranging from 3 to 12 days doubling time and also from regenerating rat liver. The ferritins from all six tumors differed electrophoretically from normal rat liver ferritin. Five of them migrated identically, and antigenic studies on four confirmed the change in protein structure. In response to iron treatment of the host, more ferritin protein and iron accumulated in all the tumors. However, by com parison with normal liver, the ratio of iron to protein in hepatoma ferritin and the capacity for iron uptake by the tumors were both low. With increasing rate of growth, the hepatomas showed progressively less capacity for iron uptake, less ferritin iron per g tumor, and especially a diminishing iron/protein ratio of tumor ferritin. Regenerating liver also showed a lower ferritin iron content but had an increased capacity for uptake of 59Fe, and its ferritin was