MITOCHONDRIAL RESPIRATORY-CHAIN FUNCTION IN MULTIPLE SYSTEM ATROPHY

Multiple system atrophy (MSA) is a clinicopathological entity distinct from idiopathic Parkinson's disease (PD) that is responsible for 5-10 % of cases of parkinsonism. Degeneration of nigral neurones is a featu re of both diseases. A specific deficiency of mitochondrial complex I activity has been found in PD substantia nigra. We have analysed mitoc hondrial function in substantia nigra and platelets from MSA patients to identify any respiratory chain defect in this disorder and to deter mine its tissue specificity. As our MSA patients had been on L-DOPA, w e also sought to establish whether this treatment could cause the comp lex I defect as seen in PD. We found no significant difference in resp iratory chain activity corrected for mitochondrial mass between contro l and MSA patients in either of the tissues studied. These results pro vide a biochemical dimension to the differences between MSA and idiopa thic PD. In addition, the fact that L-DOPA failed to induce a complex I defect in MSA substantia nigra suggests that this treatment is unlik ely to cause the complex I deficiency in PD, without additional factor s that may operate in PD.