Uptake of triclopyr (3,5,6-trichloro-2-pyridinyloxyacetic acid) and dicamba (3,6-dichloro-2-methoxybenzoic acid) from the apical membranes of the human intestinal Caco-2 cells

摘要

We investigated whether the uptake of triclopyr (3, 5, 6-trichloro-2-pyridinyloxyacetic acid) and dicamba (3,6-dichloro-2-methoxybenzoic acid) across the apical membrane of Caco-2 cells was mediated via proton-linked monocarboxylic acid transporters (MCTs). The uptake of triclopyr from the apical membranes was fast, pH-, temperature-, and concentration dependent, required metabolic energy to proceed, and was competitively inhibited by monocarboxylic acids such as benzoic acid and ferulic acid (substrates of l-lactic acid-insensitive MCTs), but not by l-lactic acid. Thus, the uptake of triclopyr in Caco-2 cells appears to be mediated mainly via l-lactic acid-insensitive MCTs. In contrast, the uptake of dicamba (a benzoic acid derivative) was slow, and it was both pH- and temperature dependent. Coincubation with ferulic acid did not decrease the uptake of dicamba, although coincubation with benzoic acid moderately decreased it. The uptake of dicamba appears to be mediated mainly via passive diffusion, which is in contrast to the uptake of benzoic acid via MCTs. We speculate that the substituted groups in dicamba may inhibit uptake via MCTs.