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  • 1
    Electronic Resource
    Electronic Resource
    Effect of the cationic polypeptide polylysine on neutral amino acid transport in isolated brain microvessels (1992)
    Springer
    Amino acids 3 (1992), S. 253-260 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Cationic polypeptide ; Blood brain barrier ; Neutral amino acids transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The functionality of isolated brain microvessels — used as anin vitro model of the blood-brain barrier — can be influenced by interaction with cationic proteins. The various polylysines (Mr ranging from 0.9 to 180 kDa) tested affected the activity of both the Na+-dependent (“A”) and the Na+-independent (“L”) systems for neutral amino acid transport. Exposure to the 180 kDa polylysine caused a conspicuous inhibition of both transport systems, associated to an increased passive permeability. There was a constant, Mr-dependent, inhibition of the the L-system-mediated uptake of hydrophobic neutral amino acids. The activity of the A-system was enhanced, upon exposure to polymers larger than 22 kDa reaching its peak at 68 kDa and and declining at higher Mr values. The effect which was Na+-ions dependent and abolished by phloretine, could be essentially ascribed to an increased affinity of the MeAIB for its carrier (Km value decreasing from 265 to 169µM in presence of 68 kDa polylysine).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806000
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Synergism between different transport systems stimulates the uptake of neutral amino acids by isolated brain microvessels (1992)
    Springer
    Amino acids 2 (1992), S. 13-23 
    Details
    ISSN: 1438-2199
    Keywords: Amino acid transport ; Blood-brain barrier ; Glutamine ; Methionine ; Methanethiol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The polar long-chain amino acids glutamine and methionine can be transported across the endothelial cells of brain microvessels either by an L-system which operates by a facilitated diffusion, exchanging mechanism, or by a concentrating, energy-dependent A-system. The presence of glutamine and/or of methionine can induce a synergism between the two transport systems which results, by a transstimulation mechanism, in a net increased uptake of neutral hydrophobic aminoacids. The methionine analog S-methylthiocysteine, which is the mixed disulfide resulting from the combination of methanethiol with cysteine, behaves similarly to methionine in stimulating the uptake of neutral hydrophobic amino acids. The same transstimulating effect can even be obtained in collagenase-treated, A-system-deprived microvessels by inducing the direct formation of S-methylthiocysteine within the cytoplasmic compartment of the endothelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806074
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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