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Monocarboxylate transporter (MCT)‐mediated transport of γ‐hydroxybutyric acid in human intestinal Caco‐2 cells
Author(s) -
Felmlee Melanie Ann,
Lam Wing Ki,
Morris Marilyn E.
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.747.3
Subject(s) - caco 2 , transporter , chemistry , sodium , symporter , cotransporter , kinetics , messenger rna , microbiology and biotechnology , biochemistry , monocarboxylate transporter , cell , biology , gene , physics , organic chemistry , quantum mechanics
Purpose To evaluate the expression of monocarboxylate transporters (MCTs) 1‐4 and characterize the intestinal transport of the known MCT substrates, γ‐hydroxybutyric acid (GHB) and D‐lactate. Methods The mRNA and protein expression of MCT1‐4 were determined by RT‐PCR and western blotting. GHB and D‐lactate uptake and directional flux kinetics were analyzed in Caco‐2 cells. Transport properties were determined with specific inhibitors and different pH and sodium conditions. Results MCT1‐4 mRNA was expressed in Caco‐2 cells; however, protein expression was observed for only MCT1, 2 and 4. GHB and D‐lactate uptake was pH‐ and concentration‐dependent, but sodium‐independent. Uptake was characterized by simple Michaelis‐Menton kinetics. Km, and Vmax estimates were 42.9 ± 9.4 mM, and 57.6 ± 10.3 nmol/mg/min for GHB. GHB was transported primarily in the apical to basolateral direction and was inhibited by the known MCT inhibitor α‐cyano‐4‐hydroxycinnamate, consistent with the apical localization of MCTs. Conclusions MCTs contribute significantly to the transport of GHB in Caco‐2 cells. Further studies are needed to determine the contributions of MCT1, 2 and 4 to the intestinal transport of GHB. Support NIH grant DA023223 and a fellowship for MAF from Pfizer Inc.