Renal dopamine excretion in healthy volunteers after oral ingestion of L-dopa.
L-Dopa is converted to dopamine by aromatic-L-amino acid decarboxylase (AADC). In the kidney, proximal tubular epithelial cells are rich in AADC and urinary free dopamine excretion is a marker for endorenal extraneuronal dopamine synthesis. The urinary free dopamine excretion was analysed in a double-blind cross-over study after oral ingestion of L-Dopa or a placebo in five healthy volunteers. The drug ingestions were separated by one week's wash-out. Since in a preliminary study, two volunteers ingesting a single L-Dopa dose of 500 mg with breakfast experienced nausea, the five volunteers of the present study were given 300 mg L-Dopa (50 mg at 9 am with breakfast, 100 mg before lunch and 150 mg before dinner) without any adverse effects. L-Dopa induced an increase in 24-h urinary dopamine excretion (HPLC with electrochemical detection). Free urinary dopamine (1900 micrograms/24 h) accounted for 0.8% of the daily oral L-Dopa dose and represented 10% of total urinary dopamine excretion. L-Dopa treatment had no significant effect on mean ambulatory arterial blood pressure and heart rate measured from 9 am to 6 pm (Spacelabs) or on 24 h urinary water and sodium excretion.
Barthelmebs
M
M
Institut de Pharmacologie, URA DO589 CNRS, Faculté de Médecine, Strasbourg, France.
Mbou
P
P
Stephan
D
D
Grima
M
M
Imbs
J L
JL
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D004231:Diuresis / Q000187:drug effects; D004298:Dopamine / Q000652:urine*; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007980:Levodopa / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology; D008297:Male; D009318:Natriuresis / Q000187:drug effects
D007980:Levodopa; D004298:Dopamine