Objectives: We sought to determine concentrations of total and labile iron in substantia nigra from patients with Parkinson disease and from controls to assess if oxidative stress is triggered by an increased concentration of iron.
Methods: Total iron concentration in the whole substantia nigra was evaluated in 17 parkinsonian and 29 control samples. Concentrations of labile iron and copper were assessed in 6 parkinsonian and 8 control samples. The total iron concentration, the Fe(2+)/Fe(3+) ratio, and iron-binding compounds were determined by Mössbauer spectroscopy. Labile iron and copper were measured by electrothermal atomic absorption spectrometry. Activity of reactive oxygen species was evaluated by visible light fluorescence.
Results: The labile iron concentration was significantly higher and corresponded to significantly higher reactive oxygen species activity in parkinsonian vs control samples. No significant difference was found in the total concentrations of copper or iron in the whole substantia nigra between parkinsonian and control samples. Mössbauer spectroscopy detected no Fe(2+) in any samples.
Conclusions: The substantia nigra of parkinsonian patients contained more labile iron compared with that of controls. This labile iron generated higher reactive oxygen species activity. The oxidative stress damage in parkinsonian substantia nigra may be related to an excess of labile iron and not of the total iron in the diseased tissue.