Objective: The aims of this study were to determine the effects of heavy metals such as manganese on nicotinamide
N-methyltransferase (EC 2.1.1.1) (NNMT) activity and to consider the possibility of involvement of NNMT activation in the pathogenesis of heavy metal induced Parkinson’s disease.
Methods: NNMT activity in supernatants separated from brain, liver and kidney homogenates of 5 elderly male Wistar rats by centrifugation were measured by high performance liquid chromatography system with fluorescence. NNMT activity under the conditon of 0.5 or 5.0 mM Mn
2+, Fe
2+, Cu
2+ or Cd
2+ was compared with control (no metal ion existence).
Results: NNMT activities in rat brain, liver and kidneys were significantly decreased by Cu
2+, and those in the liver and kidneys were significantly decreased by Cd
2+. Mn
2+ reduced NNMT activity only in the liver. Fe
2+ had no effect on NNMT activity.
Conclusions: No metal increased NNMT activity in this study, contrary to our hypothesis. Further study is needed to clarify the reason why the effects of Mn
2+ and Fe
2+ which have a high relevance to Parkinson’s disease on NNMT activity differ from those of Cu
2+ and Cd
2+.
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