Uptake of 4-chloro-2-methylphenoxyacetic acid (MCPA) from the apical membrane of Caco-2 cells by the monocarboxylic acid transporter

Journal Article · Sat Mar 15 04:00:00 EDT 2008 · Toxicology and Applied Pharmacology

DOI:https://doi.org/10.1016/j.taap.2007.10.028· OSTI ID:21077947

Kimura, Osamu; Tsukagoshi, Kensuke ^[1]; Endo, Tetsuya ^[1]

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1. Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, 1757 Ishikari-Tobetsu, Hokkaido 061-0293 (Japan)

The cellular uptake mechanism of 4-chloro-2-methylphenoxyacetic acid (MCPA), a phenoxyacetic acid derivative, was investigated using Caco-2 epithelial cells. The cells were incubated with 50 {mu}M MCPA at pH 6.0 and 37 deg. C, and the uptake of MCPA from the apical membranes was measured. The uptake of MCPA was significantly decreased by incubation at low temperature (4 {sup o}C) and markedly increased by lowering the extracellular pH. Pretreatment with a protonophore, carbonylcyanide-p-(trifluoromethoxy)phenylhydrazone (25 {mu}M), or metabolic inhibitors, 2,4-dinitrophenol (1 mM) and sodium azide (10 mM), significantly decreased the uptake of MCPA by 53%, 45% and 48%, respectively. Coincubation of MCPA with 10 mM L-lactic acid or {alpha}-cyano-4-hydroxycinnamate, which is a substrate or an inhibitor of the monocarboxylic acid transporters (MCTs), significantly decreased the uptake of MCPA by 31% and 20%, respectively, and coincubation with benzoic acid profoundly decreased the uptake by 68%. In contrast, coincubation with succinic acid (a dicarboxylic acid) did not affect the uptake. Kinetic analysis of initial MCPA uptake suggested that MCPA is taken up via a carrier-mediated process [K{sub m} = 1.37 {+-} 0.15 mM, V{sub max} = 115 {+-} 6 nmol (mg protein){sup -1} (3 min){sup -1}]. Lineweaver-Burk plots show that benzoic acid competitively inhibits the uptake of MCPA with a K{sub i} value of 4.68 {+-} 1.76 mM. A trans-stimulation effect on MCPA uptake was found in cells preloaded with benzoic acid. These results suggest that the uptake of MCPA from the apical membrane of Caco-2 cells is mainly mediated by common MCTs along with benzoic acid but also in part by L-lactic acid.

• OSTI ID: 21077947
• Journal Information: Toxicology and Applied Pharmacology, Journal Name: Toxicology and Applied Pharmacology Journal Issue: 3 Vol. 227; ISSN TXAPA9; ISSN 0041-008X
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
AZIDES
BENZOIC ACID
CELL MEMBRANES
DINITROPHENOL
LACTIC ACID
PH VALUE
PROTEINS
SODIUM
STIMULATION
SUCCINIC ACID
UPTAKE