Red cell phenylalanine is not available for transport through the blood-brain barrier.
The possibility that red cell-sequestered amino acids such as phenylalanine are available for transport through the brain capillary wall, i.e., the blood-brain barrier (BBB), in vivo was investigated in the present studies with the carotid artery injection technique. Control studies included the examination of the availability of red cell-sequestered solutes such as phenylalanine or D-glucose to liver cells in vivo using a portal vein injection technique. The results show that red cell-sequestered phenylalanine is not available for transport through the BBB or into rat liver in vivo, but human red cell-sequestered D-glucose is available for uptake by liver following portal injection. Therefore, given favorable kinetics it is possible for red cell-sequestered solute to be available for uptake by tissues. However, in the case of neutral amino acids such as phenylalanine, red cell-sequestered amino acid is not available for transport through the BBB in vivo.
Ellison
S
S
Department of Medicine, UCLA School of Medicine 90024.
Pardridge
W M
WM
D000818:Animals; D001682:Biological Availability; D001692:Biological Transport; D001786:Blood Glucose / Q000032:analysis; D001812:Blood-Brain Barrier; D004912:Erythrocytes / Q000378:metabolism*; D005947:Glucose / Q000493:pharmacokinetics; D008099:Liver / Q000166:cytology / Q000378:metabolism; D010649:Phenylalanine / Q000097:blood* / Q000493:pharmacokinetics
D001786:Blood Glucose; D010649:Phenylalanine; D005947:Glucose