Delta-aminolevulinic acid transport through blood-brain barrier

1. Delta-aminolevulinic acid (ALA) and gamma-aminobutyric acid (GABA) transport through the rat blood-brain barrier (BBB) was studied. 2. GABA transport (Km=3.2+/-0.1 microM and Vmax=0.299+/-0.045 micromol/mg protein min) is probably mediated by a permease similar to Saccharomyces cerevisiae PUT4; this result also indicates that the isolated capillaries are metabolically active. 3. ALA incorporation into rat brain endothelial cells is not detected even in capillaries treated to expose the luminal surface. 4. Previous evidence indicates that ALA can cross the BBB from blood to brain; so we conclude that, with the methodology used here, transport in the luminal membrane of the capillaries cannot be investigated.