title: An active transport system in the blood-brain barrier may reduce levodopa availability.
abstract: Levodopa, the primary drug used to treat patients with Parkinson's disease, is transported into the brain by the facilitative amino acid transporter (L1). We present here an unanticipated discovery: levodopa may be pumped out of the brain by a Na(+)-dependent transport system that couples the naturally occurring Na(+) gradient existing between the brain's extracellular fluid and the cytoplasm of capillary endothelial cells. The activity of this system reduces the net availability of levodopa.
authors.affiliation: Department of Physiology and Biophysics, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA. Richard.Hawkins@rosalindfranklin.edu
authors.forename: Richard A
authors.initials: RA
authors.lastname: Hawkins
authors.forename: Ashwini
authors.initials: A
authors.lastname: Mokashi
authors.forename: Ian A
authors.initials: IA
authors.lastname: Simpson
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology*; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology; D002417:Cattle; D015259:Dopamine Agents / Q000493:pharmacokinetics*; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects; D045604:Extracellular Fluid / Q000187:drug effects; D007532:Isoleucine / Q000378:metabolism; D007980:Levodopa / Q000493:pharmacokinetics*; D008954:Models, Biological; D012964:Sodium / Q000378:metabolism; D013997:Time Factors; D014316:Tritium / Q000493:pharmacokinetics
chemical_list: D015259:Dopamine Agents; D007532:Isoleucine; D014316:Tritium; D007980:Levodopa; D012964:Sodium