Reduced platelet glutamate uptake in Parkinson's disease

Defects in mitochondrial enzymes have been found not only in substantia nig ra, but also in platelets from Parkinson's Disease (PD) patients, suggestin g a systemic impairment of energy metabolism. Since platelets present an en ergy-dependent glutamate uptake similar to that described in central nervou s system, glutamate uptake was determined in platelets from 34 PD patients and 21 age-related normal controls, as Na+-dependent [H-3]glutamate influx; glutamate level was also analyzed by reverse-phase HPLC. A 50% reduction o f glutamate uptake (p < 0.001) was observed in idiopathic PD patients, resp ect to controls and secondary parkinsonian syndromes. The decrease correlat ed with the severity of PD, measured by the UPDRS (r = -0.54; P < 0.05). Gl utamate level was increased in platelets of PD patients, but was not correl ated to the uptake decrease. Both phoenomena may be explained by the modifi cations of mitochondrial enzymes described in platelets, which could be use d as a peripheral model of glutamatergic function in PD.