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P‐glycoprotein and multidrug resistance‐associated protein (MRP) reverse the intestinal transport of L‐DOPA, a LAT2 substrate
Author(s) -
Fraga Sónia,
SoaresdaSilva Patricio
Publication year - 2006
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.20.5.a841-c
Subject(s) - efflux , p glycoprotein , caco 2 , extracellular , transporter , chemistry , epithelial polarity , substrate (aquarium) , in vitro , cell , biochemistry , multiple drug resistance , biology , gene , ecology , antibiotics
Recently, the Na+‐independent and pH‐sensitive hetero amino acid exchanger LAT2 was shown to be a L‐DOPA transporter in renal tissues, whose activation results in trans‐stimulation of L‐DOPA outward transfer (Faseb J 18, 1489–1498, 2004). The mechanism of transepithelial L‐DOPA transport was studied in polarized Caco‐2 cells, an in vitro model of human intestinal epithelium. [14C]‐L‐DOPA was efficiently transported at both poles of the cell. However, the flux in the apical‐to‐basolateral direction was twice that in basolateral‐to‐apical direction, suggesting an asymmetric distribution of L‐DOPA transporter units in the apical and basolateral cell borders. The efflux of [14C]‐L‐DOPA was a trans‐stimulable process, markedly increased by the presence of L‐DOPA or L‐leucine in the apical and basolateral cell side. [14C]‐L‐DOPA outward was also a pH‐sensitive process as lowering extracellular pH promoted L‐DOPA‐stimulated [14C]‐L‐DOPA outflow, particularly at the apical cell side. Involvement of P‐glycoprotein (P‐gp) and multidrug resistance‐associated protein (MRP) in [14C]‐L‐DOPA efflux was also investigated. The results obtained show that verapamil (100 μM) and MK‐571 (50 μM), inhibitors of respectively P‐gp and MRP, significantly inhibited (by ~ 50%) the spontaneous [14C]‐L‐DOPA outward transfer. These findings suggest that L‐DOPA is transported across Caco‐2 cells by the pH‐sensitive and trans‐stimulable L‐type amino acid transporter 2 (LAT2). L‐DOPA is also a substrate for P‐gp and MRP. Supported by grant POCTI/SAU‐OBS/57916/2004.