The role of monoamine oxidase, iron-melanin interaction, and intracellular calcium in Parkinson's disease.

Recent evidence suggests that iron accumulates in substantia nigra pars compacta of patients with Parkinson's disease (PD). This finding is compatible with changes in the respiratory chain activity, increase of malondialdehyde concentration (a measure of lipid peroxidation), decrease of enzyme activity of enzymes involved in detoxication of hydrogen peroxide and oxygen radical species, increased MAO-B-activity in this brain area etc. All these data suggest that oxidative stress may play a certain role in the pathobiochemistry of PD. In addition to the description of the neuroprotective mechanism of the MAO-B-inhibitor L-deprenyl a new aspect focuses the role of the endogenous MAO-B substrates "polyamines" which occur both in neurons and glia. A further aspect of this review deals with the role of calcium as cellular toxin. Although of major importance it is not decided yet whether these biochemical changes are primary or secondary importance to the pathogenesis of PD.