Non-transferrin-bound-iron in serum and low-molecular-weight-iron in the liver of dietary iron-loaded rats.

1. The feeding of 0.5% (3,5,5-trimethylhexanoyl)ferrocene (TMH-ferrocene) in rats resulted in a severe and progressive liver siderosis (total liver iron, 30 mg/g liver wet weight, after 30 weeks). 2. High concentrations of an iron-rich ferritin (up to 250 mg/l) were detected in serum of heavily iron-loaded rats forming a large fraction of non-transferrin-bound-iron (5000 micrograms/dl in maximum). 3. Ferritin and not haemosiderin was the major iron storage protein in the liver. 4. The total liver iron concentration (from 0.4 to > 30 mg Fe/g wet wt) but not the cytosolic low-molecular-weight-iron fraction (from 0.5 to 2.5 microM) was extremely increased during iron-loading.