Chemical speciation of iron deposits in thalassemic heart tissue

Heart tissue from beta-thalassemia/hemoglobin E patients was taken at autop sy. The patients had received no blood transfusions or iron chelation thera py. Ferritin and hemosiderin were isolated from the tissue and studied usin g Fe-57 Mossbauer spectroscopy, transmission electron microscopy and electr on diffraction. The ferritin was shown to contain mineral cores with a mean particle site of 7.37 (s.d. 0.84) nm. Electron diffraction and Mossbauer s pectroscopy indicated that the cores had structures based on that of the mi neral ferrihydrite and were superparamagnetic with a mean blocking temperat ure of 34 K on the Mossbauer measurement time scale. The hemosiderin partic les ranged in size from 1 to 10 nm and were indicated to have a very poor c rystalline structure. Mossbauer spectroscopic measurement indicated that th e majority of the iron in the hemosiderin was paramagnetic/superparamagneti c at 4.2 K. Mossbauer spectroscopy of the heart tissue indicted that approx imately 40% of the tissue iron is in the form of hemosiderin, 35% in the fo rm of ferritin, 3% in the form of heme iron, and approximately 20% in the f orm of an unidentified form of iron that yields a spectral singlet with cen tre shift of 0.32 mm s(-1) at 15 K with respect to alpha-iron at room tempe rature. (C) 2000 Elsevier Science S.A. All rights reserved.