FURTHER CHARACTERIZATION OF FORMS OF HEMOSIDERIN IN IRON-OVERLOADED TISSUES

The biochemical and biophysical properties of isolated haemosiderins h ave been compared to that of another iron-containing protein, termed p rehaemosiderin, which sediments through chaotropic potassium iodide on ly after 20 h of ultracentrifugation, in contrast to that of haemoside rin which is recovered after 2 h of ultracentrifugation. The iron/prot ein ratio and iron/phosphate ratio were less that that of the correspo nding haemosiderin, while the elemental composition was also reduced i n many of the prehaemosiderin samples. Mossbauer spectroscopy and elec tron diffraction identified the predominant presence of ferrihydrite i n prehaemosiderin species even though the secondary haemochromatosis h aemosiderin iron cores were essentially goethite-like. The majority of the prehaemosiderins isolated showed the presence of an additional pe ptide band at 17 kDa in addition to that at 21 kDa. Further Mossbauer studies of haemosiderin isolated from untreated secondary haemochromat osis patients showed that goethite was the predominant form of iron pr esent, thereby indicating that the presence of this form of ferrihydri te was not wholly attributable to chelation therapy.