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  • Title: Evidence for an asymmetrical uptake of L-carnitine in the blood-brain barrier in vitro.
    Author: Mroczkowska JE, Galla HJ, Nalecz MJ, Nalecz KA.
    Journal: Biochem Biophys Res Commun; 1997 Dec 08; 241(1):127-31. PubMed ID: 9405245.
    Abstract:
    The transport of L-carnitine (4-N-trimethylammonium-3-hydroxybutyric acid) was studied with a primary culture of porcine brain capillary endothelial cells (BCEC) as an in vitro model of the blood-brain barrier. The measurements with suspended cells and cell monolayers allowed to distinguish a polarized transport phenomena. The part of the BCEC cells exposed to the medium (apical membrane) accumulated carnitine by a sodium-independent, saturable (Km=28 microM) system, with k=0.018 min-1. Exposure of the basolateral part revealed a presence of a facilitated diffusion process. Carnitine uptake through the saturable system was inhibited by butyrobetaine. Acylcarnitines and choline have no effect on the carnitine accumulation in suspended cells, a process diminished by phenylalanine, leucine, and L system inhibitor. This points to the possibility that carnitine enters through the basolateral membrane using amino acid transporting systems. A different, novel system is postulated to operate in the apical part of the plasma membrane of BCEC.
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