Human nigral and liver iron — comparison by Mössbauer spectroscopy, electron microscopy and ELISA

Abstract

The properties of iron present in human liver and human substantia nigra (SN) were compared. Mössbauer measurements have shown that iron is present in similar concentrations in SN and in the liver, mainly as ferritin-like iron. The size of the iron cores of ferritin, as obtained from electron microscopy, is much smaller in SN (3.6±0.4 nm) than in liver (5.7±0.5 nm). The small size in SN is in agreement with the low blocking temperature (about 10 K), determined by temperature dependent Mössbauer studies on whole tissues. ELISA studies have shown differences between SN and liver in the structures of the protein shells of ferritin. The H/L ratio (concentration of heavy to light chains) in liver is 0.40±0.02, while in SN it is 4.3±0.3. Another possible iron binding compound in SN is neuromelanin (NM). Mössbauer studies of neuromelanin, isolated from 22 SNs, demonstrated that this iron is superparamagnetic. The blocking temperature found for this neuromelanin iron is however much higher than that for ferritin.