Carrier-mediated transport of folic acid in BeWo cell monolayers as a model of the human trophoblast.
Using cultured BeWo cells as a model of human trophoblast, we investigated whether carrier-mediated transport of folic acid occurs. BeWo cells, which were derived from human choriocarcinoma, were cultured on a tissue culture plate or in a permeation chamber. When the cells reached confluence, drug uptake or transport experiments were performed. The uptake of [(3)H]folic acid by BeWo cells occurred at a much lower rate at 4 degrees C than at 37 degrees C. The uptake of [(3)H]folic acid was saturable at higher concentrations and inhibited by typical metabolic inhibitors, sodium azide and 2,4-dinitrophenol. The uptake of [(3)H]folic acid was significantly increased with decreasing pH of the incubation buffer and markedly inhibited by 4,4'-diidothiocyanostilbene-2,2'-disulfonic acid (DIDS). Analogs of folic acid, methotrexate and 5-methyltetrahydrofolate, inhibited the uptake of [(3)H]folic acid by BeWo cells. Kinetic analysis using Lineweaver-Burk plots revealed that methotrexate competitively inhibited the uptake of [(3)H]folic acid and folic acid competitively inhibited the uptake of [(3)H]methotrexate. In transport experiments, the permeation of [(3)H]folic acid from the apical-to-basal side was greater than that from the basal-to-apical side, and the transport of [(3)H]folic acid from the apical-to-basal side was inhibited by an excess of folic acid. The findings obtained in the present study confirm the existence of an asymmetric, carrier-mediated transport system for folic acid and its analog, methotrexate, across BeWo cells, a representative of the human trophoblast.
Takahashi
T
T
Department of Pharmaceutics and Biopharmaceutics, Showa Pharmaceutical University, Machida, Tokyo 194-8543, Japan.
Utoguchi
N
N
Takara
A
A
Yamamoto
N
N
Nakanishi
T
T
Tanaka
K
K
Audus
K L
KL
Watanabe
Y
Y
D019297:2,4-Dinitrophenol / Q000494:pharmacology; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000838:Anions; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D004734:Energy Metabolism; D005260:Female; D005492:Folic Acid / Q000378:metabolism*; D005493:Folic Acid Antagonists / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008727:Methotrexate / Q000494:pharmacology; D008954:Models, Biological; D011247:Pregnancy; D019810:Sodium Azide / Q000494:pharmacology; D013696:Temperature; D013763:Tetrahydrofolates / Q000494:pharmacology; D014316:Tritium; D014327:Trophoblasts / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014475:Uncoupling Agents / Q000494:pharmacology
D000838:Anions; D002352:Carrier Proteins; D005493:Folic Acid Antagonists; D013763:Tetrahydrofolates; D014475:Uncoupling Agents; D014316:Tritium; D005492:Folic Acid; D019810:Sodium Azide; D019297:2,4-Dinitrophenol; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C005984:5-methyltetrahydrofolate; D008727:Methotrexate