The effect of prolonged iron loading on the chemical form of iron oxide deposits in rat liver and spleen.

Female Porton rats were loaded with iron either by supplementing the diet with 2.5% carbonyl iron for up to 22 months (18 rats) or by regularly injecting rat blood cells intraperitoneally for up to 10 months (eight rats). 57Fe Mössbauer spectroscopy of freeze-dried samples of liver and spleen was used to analyse the chemical forms of iron deposited in these tissues over the period of iron loading. A sextet signal in the Mössbauer spectra was identified as being due to a form of haemosiderin based on the structure of the mineral goethite. The spectral parameters of the sextet signal in the rat tissues indicate that the goethite-like haemosiderin particles are less crystalline than those found in iron-loaded human tissues. For the dietary-iron-loaded rat livers, the fraction (Fs) of the Mössbauer signal in the form of this sextet was found to increase significantly (from approx 0.04 to 0.09) with the age of the rats (r=0.77, P<0.0005). This indicates that the fraction of liver iron in the form of the goethite-like haemosiderin increases with age of the rat and hence with the duration of iron loading. In addition, Fs for these livers was found to increase significantly with the fraction of iron in non-parenchymal cells as measured by computer-assisted morphometric analysis of histological sections (r=0.71, P<0.005).