Studies on haemosiderin and ferritin from iron-loaded rat liver

Abstract

Haemosiderin has been isolated from siderosomes and ferritin from the cytosol of livers of rats iron-loaded by intraperitoneal injections of iron-dextran. Siderosomal haermosiderin, like ferritin, was shown by electron diffraction to contain iron mainly in the form of small particles of ferrihydrite (5Fe2O3.9H2O), with average particle diameter of 5.36 +/- 1.31 nm (SD), less than that of ferritin iron-cores (6.14 +/- 1.18 nm). Mössbauer spectra of both iron-storage complexes are also similar, except that the blocking temperature, TB, for haemosiderin (23 K) is lower than that of ferritin (35 K). These values are consistent with their differences in particle volumes assuming identical magnetic anisotropy constants. Measurements of P/Fe ratios by electron probe microanalysis showed the presence of phosphorus in rat liver haemosiderin, but much of it was lost on extensive dialysis. The presence of peptides reacting with anti-ferritin antisera and the similarities in the structures of their iron components are consistent with the view that rat liver haemosiderin arises by degradation of ferritin polypeptides, but its peptide pattern is different from that found in human beta-thalassaemia haemosiderin. The blocking temperature, 35 K, for rat liver ferritin is near to that reported, 40 K, for human beta-thalassaemia spleen ferritin. However, the haemosiderin isolated from this tissue, in contrast to that from rat liver, had a TB higher than that of ferritin. The iron availability of haemosiderins from rat liver and human beta-thalassaemic spleen to a hydroxypyridinone chelator also differed. That from rat liver was equal to or greater, and that from human spleen was markedly less, than the iron availability from either of the associated ferritins, which were equivalent. The differences in properties of the two types of haemosiderin may reflect their origins from primary or secondary iron overload and differences in the duration of the overload.

Bioinorganic transformations of liver iron deposits observed by tissue magnetic characterisation in a rat model

“…In previous studies on iron dextran administration to mice [36] and to rats [37], together with ferritin and other iron deposits, rests of the drug were still detected in the liver and spleen tissues at least until 3 weeks after the injection. For this reason, we find it necessary to describe the individual structural properties of iron dextran and ferritin prior to the interpretation of our results in tissues.…”

“…A warning was made on the use of the single term haemosiderin to identify iron containing bodies, as those coming from the digestion of physiological iron containing proteins or from administered iron compounds, whose common feature is the positive reaction under the Prussian blue test but that under TEM observations appear actually different. Since physical differences between haemosiderins corresponding to various pathological tissues [11,50] have been detected, it has been pointed out the necessity of specifying the conditions, pathology and treatments, under which these deposits have been formed [37]. Nowadays, the term haemosiderin is usually ascribed to ''a poorly defined iron-protein complex that forms an insoluble iron storage system thought to be derived from the lysosomal degradation of the ferritin protein shell'' [21].…”

Pathogenic implications of distinct patterns of iron and zinc in chronic MS lesions

“…While the mechanism of goethite formation is undefined, it is unlikely that it forms from ferritin’s ferrihydrite [10, 11]. Iron in goethite is less soluble and released less readily than iron of ferritin [2, 40, 67]. Because XFI cannot distinguish between cell types, it is conceivable that astrocytes pick up the goethite already biomineralized by macrophages, or they biomineralize the iron picked up from macrophages.…”

Iron speciation study in Hfe knockout mice tissues: Magnetic and ultrastructural characterisation

“…Mössbauer spectroscopy [4][5][6][7][8][9][10], Transmission Electron Microscopy (TEM) [11][12][13][14], infrared spectroscopy [15] and magnetic measurements [16][17][18][19][20], as the biomineralisation of iron in the tissues may be related to its toxicity. In particular, the study of the magnetic properties of these tissues is of special interest to improve noninvasive, magnetism-based, techniques for diagnosis and follow-up treatment of iron overload diseases [21][22][23][24][25][26].…”