RESPIRATORY-CHAIN ENZYME-ACTIVITIES IN ISOLATED-MITOCHONDRIA OF LYMPHOCYTES FROM UNTREATED PARKINSONS-DISEASE PATIENTS

We studied respiratory-chain enzyme activities in lymphocyte mitochond ria from 36 untreated Parkinson's disease (PD) patients and in 30 age- and sex-matched healthy controls. The respiratory-chain enzyme activi ties did not differ significantly between patients and controls. Moreo ver, no patient showed respiratory-chain enzyme levels below normal ra nge. Values for activities of complexes in the PD group did not correl ate with age at onset, duration, scores of the Unified Parkinson's Dis ease Rating scales, or Hoehn and Yahr staging. These results suggest t hat the presence of defects of respiratory-chain complexes could depen d on methodologic aspects, and that determinations of respiratory-chai n enzymes in cell homogenates are not generally appropriate for evalua ting abnormal mitochondrial dysfunction, especially when the amount of the specific enzyme is relatively low, as is the case of blood cells. In addition, the method of measuring complex I activity is critical f or evaluating the results. In conclusion, our finding of normal mitoch ondrial function in lymphocyte mitochondria suggests that this tissue cannot be used to develop a diagnostic test for PD.