title: Effects of different oxidizing agents on neutral amino acid transport systems in isolated bovine brain microvessels.
abstract: Using isolated bovine brain microvessels as an in vitro model of the blood-brain barrier (BBB) we have evaluated the role of free radical generating solutions on some amino acid transport systems operating on the endothelial cell membrane. Fe(2+)/ascorbate, phenylhydrazine and CuSO(4) did not affect any of the transport system tested, while exposure of bovine brain microvessels to tert-butylhydroperoxide (t-BHP) caused a reduced capacity to take up small neutral amino acids via the Na(+)-dependent A-system. The presence of glucose during t-BHP treatment did not prevent this inhibition, which was partially counteracted when the isolated microvessels were incubated with 5mM inosine before the oxidative stress. Incubation of the isolated capillaries with 5mM dithiothreitol, after exposure to t-BHP, resulted in a 50% recovery of the alpha-methylaminoisobutyrate (MeAIB) uptake by the A-system. Treatment with t-BHP, which had no effect on the L-system of neutral amino acid transport, caused a significant decrease of the intracellular levels of ATP, of glutathione (GSH), and of gamma-glutamyltranspeptidase (GGT) activity, while no significant modification of hexokinase (HK) or of alkaline phosphatase (ALKP) activities were observed. Oxidative damage of the BBB appears therefore to impair essentially the metabolic pathways which ensure the energy requirement for the endothelial cells, thus inhibiting the energy-dependent amino acid transport system "A".
authors.affiliation: Department of Cellular Biotechnology and Hematology, University of Rome, La Sapienza, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Cardelli
authors.forename: Sigfrido
authors.initials: S
authors.lastname: Scarpa
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Ceci
authors.forename: Marco
authors.initials: M
authors.lastname: Lucarelli
authors.forename: Fabio
authors.initials: F
authors.lastname: Tabacco
authors.forename: Giampiero
authors.initials: G
authors.lastname: Ferraguti
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Brisdelli
authors.forename: Roberto
authors.initials: R
authors.lastname: Strom
authors.forename: Argante
authors.initials: A
authors.lastname: Bozzi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D026921:Amino Acid Transport Systems, Neutral / Q000187:drug effects*; D000818:Animals; D001921:Brain / Q000098:blood supply*; D002417:Cattle; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D005978:Glutathione / Q000378:metabolism; D066298:In Vitro Techniques; D010084:Oxidation-Reduction
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D000255:Adenosine Triphosphate; D005978:Glutathione