title: The absorptive flux of the anti-epileptic drug substance vigabatrin is carrier-mediated across Caco-2 cell monolayers.
abstract: Vigabatrin is an anti-epileptic drug substance. The oral bioavailability of vigabatrin is high (60-70%), however, little is known about the mechanism(s) mediating the intestinal absorption. The aim of the present study was to identify which solute carrier(s) are involved in the absorption of vigabatrin in Caco-2 cells, a cell culture model of the small intestinal epithelium. The uptake and transepithelial flux of vigabatrin was measured using an LC-MS method for quantification. Transepithelial transport of vigabatrin was shown to be proton-dependent and polarized in the apical-to-basolateral (A-B) direction. The A-B flux of vigabatrin had a saturable component and a passive component, indicating the presence of a carrier system in parallel with a passive permeability. The Michaelis constant, Km, of the transepithelial A-B flux of vigabatrin was estimated to be 32.8±7.4 mM (n=3-5), whereas the Km of the apical uptake was found to be 12.7±3.7 mM (n=3). The carrier-mediated transepithelial A-B flux of vigabatrin accounted for 80-95% (50.0-1.0mM) of the total A-B flux. The transepithelial A-B flux (as well as apical uptake) of vigabatrin was significantly decreased upon addition of substrates or inhibitors of the human proton-coupled amino acid transporter (hPAT1) to the apical solution. The present study indicates that the transepithelial A-B flux of vigabatrin is mainly mediated by hPAT1 in Caco-2 cells at dose-relevant concentrations.
authors.affiliation: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark.
authors.forename: Martha Kampp
authors.initials: MK
authors.lastname: Nøhr
authors.forename: Steen Honoré
authors.initials: SH
authors.lastname: Hansen
authors.forename: Birger
authors.initials: B
authors.lastname: Brodin
authors.forename: René
authors.initials: R
authors.lastname: Holm
authors.forename: Carsten Uhd
authors.initials: CU
authors.lastname: Nielsen
mesh_terms: D026905:Amino Acid Transport Systems / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology*; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D004151:Dipeptides / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism; D027981:Symporters / Q000378:metabolism; D020888:Vigabatrin / Q000378:metabolism*
chemical_list: D026905:Amino Acid Transport Systems; D000596:Amino Acids; D004151:Dipeptides; C475905:SLC36A1 protein, human; D027981:Symporters; C004194:glycylsarcosine; D020888:Vigabatrin
keywords: 2-(N-morpholino)ethanesulfonic acid; 2-amino-2-norbornanecarboxylic acid; 4-(2-hydroxyethyl)-1-piperazine ethanesulphonic acid; 5-HTP; 5-hydroxy-L-tryptophan; A-B; Asp; B-A; BCH; BSA; Caco-2 cells; D-mannitol; GABA; Glu; Gly; Gly-Sar; HBSS; HEPES; Hank’s buffered salt solution; Intestinal permeability; L-aspartate; L-glutamate; L-leucine; L-lysine; L-prolin; L-tryptophan; LYAAT1; Leu; Lys; MES; MeAIB; N-methylamino isobutyric acid; Pro; SLC36A1; Sar; TC; TEER; Trp; Vigabatrin; apical to basolateral; basolateral to apical; bovine serum albumin; glycine; glycyl-sarcosine; hPAT1; hPEPT1; human proton-coupled amino acid transporter 1; human proton-coupled di- and tripeptide transporter 1; mannitol; sarcosine; taurocholic acid; transepithelial electrical resistance; α-MDG; α-methyl-D-glucopyranoside; γ-aminobutyric acid