0000000000970824
AUTHOR
Wha-joon Lee
Role of oxoproline in the regulation of neutral amino acid transport across the blood-brain barrier.
Regulation of neutral amino acid transport was studied using isolated plasma membrane vesicles derived from the bovine blood-brain barrier. Neutral amino acids cross the blood-brain barrier by facilitative transport system L1, which may allow both desirable and undesirable amino acids to enter the brain. The sodium-dependent amino acid systems A and Bo,+ are located exclusively on abluminal membranes, in a position to pump unwanted amino acids out. gamma-Glutamyl transpeptidase, the first enzyme of the gamma-glutamyl cycle, is an integral protein of the luminal membrane of the blood-brain barrier. We demonstrate that oxoproline, an intracellular product of the gamma-glutamyl cycle, stimulat…
Glutamine transport by the blood-brain barrier: a possible mechanism for nitrogen removal
Glutamine and glutamate transport activities were measured in isolated luminal and abluminal plasma membrane vesicles derived from bovine brain endothelial cells. Facilitative systems for glutamine and glutamate were almost exclusively located in luminal-enriched membranes. The facilitative glutamine carrier was neither sensitive to 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid inhibition nor did it participate in accelerated amino acid exchange; it therefore appeared to be distinct from the neutral amino acid transport system L1. Two Na-dependent glutamine transporters were found in abluminal-enriched membranes: systems A and N. System N accounted for approximately 80% of Na-dependent glu…