Expression of a system L neutral amino acid transporter at the blood-brainbarrier

Amino acid transport system L has been proposed to be one of the major nutr ient transport systems at the blood-brain barrier. Using immunohistochemica l analyses, a system L transporter LAT1 was shown to be expressed in the br ain capillary endothelial cells in rats. Because LAT1 was coexpressed with 4F2 heavy chain which brings LAT1 to the plasma membrane, LAT1 is proposed to be functional in the plasma membrane of brain capillary endothelial cell s. Both LAT1 and 4F2hc immunoreactivities were detected in-a double line ap pearance surrounding endothelial cell nuclei, suggesting both proteins are present in the luminal and abluminal membranes. LAT1 is, thus, a blood-brai n-barrier system L transporter responsible for the permeation of aromatic o r branched-chain amino acids and amino acid-related drugs such as L-DOPA. N euroReport 11:3507-3511 (C) 2000 Lippincott Williams & Wilkins.