Increased dopamine content in lymphocytes from high-dose L-Dopa-treated Parkinson's disease patients.

The intracellular (i.c.) content of dopamine and its metabolites was measured in the peripheral blood lymphocytes (PBLs) of Parkinson's disease (PD) patients and healthy controls. Catecholamine levels of PBLs were measured using capillary electrophoresis in healthy controls and PD patients receiving different doses of L-dihydroxyphenylalanine (L-Dopa). Higher i.c. dopamine content was found in lymphocytes from PD patients receiving a high dose of L-Dopa (700 +/- 30 mg/day) as compared to lymphocytes from the healthy controls (p = 0.002) and from PD patients treated with a low dose of L-Dopa (400 +/- 30 mg/day) (p = 0.022). The dihydroxyphenylacetic acid to dopamine ratio was significantly lower in the high-dose L-Dopa-treated PD patients than in the controls (p = 0.013). These findings suggest that the dopamine content and metabolism in the peripheral lymphocytes of PD patients are influenced by L-Dopa administration. This is the first study in which a dose-related effect of L-Dopa treatment was found in lymphocytes from PD patients.