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The present study aimed to determine the kinetics of l-3,4-dihydroxyphenylalanine (l-DOPA) uptake in an immortalised cell line of rat capillary cerebral endothelial cells (clones RBE 4 and RBE 4B), to define the type of interaction with 3-O-methyl-l-DOPA (3-OM-l-DOPA), sensitivity to 2-aminobicyclo(2,2,1)-heptane-2-carboxylic acid (BHC), N-(methylamino)-isobutyric acid (MeAIB) and sodium. Non-linear analysis of the saturation curves for l-DOPA and 3-OM-l-DOPA revealed in RBE 4 cells K_m values (in μM) of 72 (53, 91) and 40 (25, 57) and in RBE 4B cells K_m values (in μM) of 60 (46, 74) and 44 (13, 75), respectively. IC₅₀ values for 3-OM-l-DOPA (RBE 4, 642 [542, 759] μM; RBE 4B, 482 [475, 489] μM) obtained in the presence of a nearly saturating (250 μM) concentration of l-DOPA were greater than the corresponding K_i values (RBE 4, 143 [121, 170] μM; RBE 4B, 93 [92, 95] μM) obtained in the presence of a …