Muscle respiratory chain enzyme activities in parkinson's disease and in multisystem extrapyramidal disorders with parkinsonism as the main clinical feature.

A primary mitochondrial dysfunction has been recently hypothesized in the pathogenesis of Parkinson's disease (PD). As a matter of fact, MPTP (a drug able to induce neuronal loss in substantia nigra) is a specific inhibitor of Complex I, while controversial data on Complex I deficiency have been reported in platelets, muscle and brain of patients affected by Parkinson's disease. Here we report data on respiratory chain enzyme activities in isolated muscle mitochondria from 6 patients with classical PD (two with the hereditary form, HPD), and in 6 patients with a multisystem extrapyramidal disorder (MSED) with parkinsonsim as the main clinical feature. While histological and biochemical evidence of mitochondrial dysfunction has been detected in 1 case with PD and in 3 cases with MSED, normal results have been obtained in the other cases confirming the extreme clinical and biochemical heterogeneity of these disorders.